diff --git a/editor/libeditor/HTMLEditRules.cpp b/editor/libeditor/HTMLEditRules.cpp
index cf1b56c61447..ab9d06929fd3 100644
--- a/editor/libeditor/HTMLEditRules.cpp
+++ b/editor/libeditor/HTMLEditRules.cpp
@@ -700,6 +700,52 @@ nsresult HTMLEditRules::AfterEditInner() {
   return NS_OK;
 }
 
+EditActionResult HTMLEditor::CanHandleHTMLEditSubAction() const {
+  MOZ_ASSERT(IsEditActionDataAvailable());
+
+  if (NS_WARN_IF(Destroyed())) {
+    return EditActionResult(NS_ERROR_EDITOR_DESTROYED);
+  }
+
+  // If there is not selection ranges, we should ignore the result.
+  if (!SelectionRefPtr()->RangeCount()) {
+    return EditActionCanceled();
+  }
+
+  nsRange* range = SelectionRefPtr()->GetRangeAt(0);
+  nsINode* selStartNode = range->GetStartContainer();
+  if (NS_WARN_IF(!selStartNode)) {
+    return EditActionResult(NS_ERROR_FAILURE);
+  }
+
+  if (!IsModifiableNode(*selStartNode)) {
+    return EditActionCanceled();
+  }
+
+  nsINode* selEndNode = range->GetEndContainer();
+  if (NS_WARN_IF(!selEndNode)) {
+    return EditActionResult(NS_ERROR_FAILURE);
+  }
+
+  if (selStartNode == selEndNode) {
+    return EditActionIgnored();
+  }
+
+  if (!IsModifiableNode(*selEndNode)) {
+    return EditActionCanceled();
+  }
+
+  nsINode* commonAncestor = range->GetCommonAncestor();
+  if (NS_WARN_IF(!commonAncestor)) {
+    return EditActionResult(NS_ERROR_FAILURE);
+  }
+  if (!IsModifiableNode(*commonAncestor)) {
+    return EditActionCanceled();
+  }
+
+  return EditActionIgnored();
+}
+
 nsresult HTMLEditRules::WillDoAction(EditSubActionInfo& aInfo, bool* aCancel,
                                      bool* aHandled) {
   if (NS_WARN_IF(!CanHandleEditAction())) {
@@ -720,43 +766,20 @@ nsresult HTMLEditRules::WillDoAction(EditSubActionInfo& aInfo, bool* aCancel,
 
   AutoSafeEditorData setData(*this, *mHTMLEditor);
 
-  // Nothing to do if there's no selection to act on
-  if (NS_WARN_IF(!SelectionRefPtr()->RangeCount())) {
-    return NS_OK;
+  EditActionResult result = HTMLEditorRef().CanHandleHTMLEditSubAction();
+  if (NS_WARN_IF(result.Failed())) {
+    return result.Rv();
   }
-
-  RefPtr<nsRange> range = SelectionRefPtr()->GetRangeAt(0);
-  nsCOMPtr<nsINode> selStartNode = range->GetStartContainer();
-  if (NS_WARN_IF(!selStartNode)) {
-    return NS_ERROR_FAILURE;
-  }
-
-  if (!HTMLEditorRef().IsModifiableNode(*selStartNode)) {
+  if (result.Canceled()) {
+    if (!SelectionRefPtr()->RangeCount()) {
+      // Special case.  If there is no selection range, we do nothing here,
+      // but return as not handled nor canceled.
+      return NS_OK;
+    }
     *aCancel = true;
     return NS_OK;
   }
 
-  nsCOMPtr<nsINode> selEndNode = range->GetEndContainer();
-  if (NS_WARN_IF(!selEndNode)) {
-    return NS_ERROR_FAILURE;
-  }
-
-  if (selStartNode != selEndNode) {
-    if (!HTMLEditorRef().IsModifiableNode(*selEndNode)) {
-      *aCancel = true;
-      return NS_OK;
-    }
-
-    nsINode* commonAncestor = range->GetCommonAncestor();
-    if (NS_WARN_IF(!commonAncestor)) {
-      return NS_ERROR_FAILURE;
-    }
-    if (!HTMLEditorRef().IsModifiableNode(*commonAncestor)) {
-      *aCancel = true;
-      return NS_OK;
-    }
-  }
-
   switch (aInfo.mEditSubAction) {
     case EditSubAction::eInsertText:
     case EditSubAction::eInsertTextComingFromIME:
@@ -791,8 +814,6 @@ nsresult HTMLEditRules::WillDoAction(EditSubActionInfo& aInfo, bool* aCancel,
       return WillRemoveAbsolutePosition(aCancel, aHandled);
     case EditSubAction::eSetOrClearAlignment:
       return WillAlign(*aInfo.alignType, aCancel, aHandled);
-    case EditSubAction::eCreateOrRemoveBlock:
-      return WillMakeBasicBlock(*aInfo.blockType, aCancel, aHandled);
     case EditSubAction::eRemoveList: {
       nsresult rv = WillRemoveList(aCancel, aHandled);
       if (NS_WARN_IF(rv == NS_ERROR_EDITOR_DESTROYED) ||
@@ -820,6 +841,7 @@ nsresult HTMLEditRules::WillDoAction(EditSubActionInfo& aInfo, bool* aCancel,
       return WillRelativeChangeZIndex(-1, aCancel, aHandled);
     case EditSubAction::eIncreaseZIndex:
       return WillRelativeChangeZIndex(1, aCancel, aHandled);
+    case EditSubAction::eCreateOrRemoveBlock:
     case EditSubAction::eInsertHTMLSource:
     case EditSubAction::eUndo:
     case EditSubAction::eRedo:
@@ -1848,11 +1870,11 @@ EditActionResult HTMLEditRules::WillInsertParagraphSeparator() {
     // Insert a new block first
     MOZ_ASSERT(separator == ParagraphSeparator::div ||
                separator == ParagraphSeparator::p);
-    // FormatBlockContainer() creates AutoSelectionRestorer.
+    // FormatBlockContainerWithTransaction() creates AutoSelectionRestorer.
     // Therefore, even if it returns NS_OK, editor might have been destroyed
     // at restoring Selection.
     nsresult rv = MOZ_KnownLive(HTMLEditorRef())
-                      .FormatBlockContainer(
+                      .FormatBlockContainerWithTransaction(
                           MOZ_KnownLive(ParagraphSeparatorElement(separator)));
     if (NS_WARN_IF(rv == NS_ERROR_EDITOR_DESTROYED) ||
         NS_WARN_IF(!CanHandleEditAction())) {
@@ -1860,8 +1882,9 @@ EditActionResult HTMLEditRules::WillInsertParagraphSeparator() {
     }
     // We warn on failure, but don't handle it, because it might be harmless.
     // Instead we just check that a new block was actually created.
-    NS_WARNING_ASSERTION(NS_SUCCEEDED(rv),
-                         "HTMLEditor::FormatBlockContainer() failed");
+    NS_WARNING_ASSERTION(
+        NS_SUCCEEDED(rv),
+        "HTMLEditor::FormatBlockContainerWithTransaction() failed");
 
     firstRange = SelectionRefPtr()->GetRangeAt(0);
     if (NS_WARN_IF(!firstRange)) {
@@ -1890,10 +1913,10 @@ EditActionResult HTMLEditRules::WillInsertParagraphSeparator() {
     // Now, mNewBlockElement is last created block element for wrapping inline
     // elements around the caret position and AfterEditInner() will move
     // caret into it.  However, it may be different from block parent of
-    // the caret position.  E.g., FormatBlockContainer() may wrap following
-    // inline elements of a <br> element which is next sibling of container
-    // of the caret.  So, we need to adjust mNewBlockElement here for avoiding
-    // jumping caret to odd position.
+    // the caret position.  E.g., FormatBlockContainerWithTransaction() may
+    // wrap following inline elements of a <br> element which is next sibling
+    // of container of the caret.  So, we need to adjust mNewBlockElement here
+    // for avoiding jumping caret to odd position.
     HTMLEditorRef().TopLevelEditSubActionDataRef().mNewBlockElement =
         blockParent;
   }
@@ -4535,37 +4558,7 @@ nsresult HTMLEditRules::WillMakeDefListItem(const nsAString* aItemType,
   return NS_OK;
 }
 
-nsresult HTMLEditRules::WillMakeBasicBlock(const nsAString& aBlockType,
-                                           bool* aCancel, bool* aHandled) {
-  MOZ_ASSERT(IsEditorDataAvailable());
-  MOZ_ASSERT(aCancel && aHandled);
-
-  OwningNonNull<nsAtom> blockType = NS_Atomize(aBlockType);
-
-  // FYI: Ignore cancel result of WillInsert().
-  nsresult rv = MOZ_KnownLive(HTMLEditorRef()).WillInsert();
-  if (NS_WARN_IF(rv == NS_ERROR_EDITOR_DESTROYED)) {
-    return NS_ERROR_EDITOR_DESTROYED;
-  }
-  NS_WARNING_ASSERTION(NS_SUCCEEDED(rv), "WillInsert() failed");
-
-  *aCancel = false;
-  *aHandled = true;
-
-  // FormatBlockContainer() creates AutoSelectionRestorer.
-  // Therefore, even if it returns NS_OK, editor might have been destroyed
-  // at restoring Selection.
-  rv = MOZ_KnownLive(HTMLEditorRef()).FormatBlockContainer(blockType);
-  if (NS_WARN_IF(!CanHandleEditAction())) {
-    return NS_ERROR_EDITOR_DESTROYED;
-  }
-  if (NS_WARN_IF(NS_FAILED(rv))) {
-    return rv;
-  }
-  return NS_OK;
-}
-
-nsresult HTMLEditor::FormatBlockContainer(nsAtom& blockType) {
+nsresult HTMLEditor::FormatBlockContainerWithTransaction(nsAtom& blockType) {
   MOZ_ASSERT(IsTopLevelEditSubActionDataAvailable());
 
   if (!SelectionRefPtr()->IsCollapsed()) {
diff --git a/editor/libeditor/HTMLEditRules.h b/editor/libeditor/HTMLEditRules.h
index 781bac3e113f..0c0ddafdb0d1 100644
--- a/editor/libeditor/HTMLEditRules.h
+++ b/editor/libeditor/HTMLEditRules.h
@@ -366,18 +366,6 @@ class HTMLEditRules : public TextEditRules {
                                             bool aEntireList, bool* aCancel,
                                             bool* aHandled);
 
-  /**
-   * WillMakeBasicBlock() called before changing block style around Selection.
-   * This method actually does something with calling FormatBlockContainer().
-   *
-   * @param aBlockType          Necessary block style as string.
-   * @param aCancel             Returns true if the operation is canceled.
-   * @param aHandled            Returns true if the edit action is handled.
-   */
-  MOZ_CAN_RUN_SCRIPT
-  MOZ_MUST_USE nsresult WillMakeBasicBlock(const nsAString& aBlockType,
-                                           bool* aCancel, bool* aHandled);
-
   /**
    * Called after creating a basic block, indenting, outdenting or aligning
    * contents.  This method inserts a padding <br> element for empty last line
diff --git a/editor/libeditor/HTMLEditor.cpp b/editor/libeditor/HTMLEditor.cpp
index 75a63440a1b5..ea44054ea6f3 100644
--- a/editor/libeditor/HTMLEditor.cpp
+++ b/editor/libeditor/HTMLEditor.cpp
@@ -1798,9 +1798,9 @@ nsresult HTMLEditor::SetParagraphFormatAsAction(
                          "MakeDefinitionListItemWithTransaction() failed");
     return EditorBase::ToGenericNSResult(rv);
   }
-  nsresult rv = InsertBasicBlockWithTransaction(*tagName);
+  nsresult rv = FormatBlockContainerAsSubAction(*tagName);
   NS_WARNING_ASSERTION(NS_SUCCEEDED(rv),
-                       "InsertBasicBlockWithTransaction() failed");
+                       "FormatBlockContainerAsSubAction() failed");
   return EditorBase::ToGenericNSResult(rv);
 }
 
@@ -2264,7 +2264,7 @@ nsresult HTMLEditor::MakeDefinitionListItemWithTransaction(nsAtom& aTagName) {
   return NS_OK;
 }
 
-nsresult HTMLEditor::InsertBasicBlockWithTransaction(nsAtom& aTagName) {
+nsresult HTMLEditor::FormatBlockContainerAsSubAction(nsAtom& aTagName) {
   MOZ_ASSERT(IsEditActionDataAvailable());
 
   if (!mRules) {
@@ -2276,75 +2276,37 @@ nsresult HTMLEditor::InsertBasicBlockWithTransaction(nsAtom& aTagName) {
   // Protect the edit rules object from dying
   RefPtr<TextEditRules> rules(mRules);
 
-  bool cancel, handled;
-
   AutoPlaceholderBatch treatAsOneTransaction(*this);
   AutoEditSubActionNotifier startToHandleEditSubAction(
       *this, EditSubAction::eCreateOrRemoveBlock, nsIEditor::eNext);
 
-  nsDependentAtomString tagName(&aTagName);
-  EditSubActionInfo subActionInfo(EditSubAction::eCreateOrRemoveBlock);
-  subActionInfo.blockType = &tagName;
-  nsresult rv = rules->WillDoAction(subActionInfo, &cancel, &handled);
-  if (cancel || NS_FAILED(rv)) {
+  EditActionResult result = CanHandleHTMLEditSubAction();
+  if (result.Canceled() || NS_WARN_IF(result.Failed())) {
+    return result.Rv();
+  }
+
+  // FYI: Ignore cancel result of WillInsert() since we've already checked
+  //      whether we can or cannot edit current selection range.
+  nsresult rv = WillInsert();
+  if (NS_WARN_IF(rv == NS_ERROR_EDITOR_DESTROYED)) {
+    return NS_ERROR_EDITOR_DESTROYED;
+  }
+  NS_WARNING_ASSERTION(NS_SUCCEEDED(rv), "WillInsert() failed, but ignored");
+
+  // FormatBlockContainerWithTransaction() creates AutoSelectionRestorer.
+  // Therefore, even if it returns NS_OK, editor might have been destroyed
+  // at restoring Selection.
+  rv = FormatBlockContainerWithTransaction(aTagName);
+  if (NS_WARN_IF(Destroyed())) {
+    return NS_ERROR_EDITOR_DESTROYED;
+  }
+  if (NS_WARN_IF(NS_FAILED(rv))) {
     return rv;
   }
 
-  if (!handled && SelectionRefPtr()->IsCollapsed()) {
-    nsRange* firstRange = SelectionRefPtr()->GetRangeAt(0);
-    if (NS_WARN_IF(!firstRange)) {
-      return NS_ERROR_FAILURE;
-    }
-
-    EditorDOMPoint atStartOfSelection(firstRange->StartRef());
-    if (NS_WARN_IF(!atStartOfSelection.IsSet()) ||
-        NS_WARN_IF(!atStartOfSelection.GetContainerAsContent())) {
-      return NS_ERROR_FAILURE;
-    }
-
-    // Have to find a place to put the block.
-    EditorDOMPoint pointToInsertBlock(atStartOfSelection);
-
-    while (!CanContainTag(*pointToInsertBlock.GetContainer(), aTagName)) {
-      pointToInsertBlock.Set(pointToInsertBlock.GetContainer());
-      if (NS_WARN_IF(!pointToInsertBlock.IsSet()) ||
-          NS_WARN_IF(!pointToInsertBlock.GetContainerAsContent())) {
-        return NS_ERROR_FAILURE;
-      }
-    }
-
-    if (pointToInsertBlock.GetContainer() !=
-        atStartOfSelection.GetContainer()) {
-      // We need to split up to the child of the point to insert a block.
-      SplitNodeResult splitBlockResult = SplitNodeDeepWithTransaction(
-          MOZ_KnownLive(*pointToInsertBlock.GetChild()), atStartOfSelection,
-          SplitAtEdges::eAllowToCreateEmptyContainer);
-      if (NS_WARN_IF(splitBlockResult.Failed())) {
-        return splitBlockResult.Rv();
-      }
-      pointToInsertBlock = splitBlockResult.SplitPoint();
-      if (NS_WARN_IF(!pointToInsertBlock.IsSet())) {
-        return NS_ERROR_FAILURE;
-      }
-    }
-
-    // Create a block and insert it before the right node if we split some
-    // parents of start of selection above, or just start of selection
-    // otherwise.
-    RefPtr<Element> newBlock =
-        CreateNodeWithTransaction(aTagName, pointToInsertBlock);
-    if (NS_WARN_IF(!newBlock)) {
-      return NS_ERROR_FAILURE;
-    }
-
-    // reposition selection to inside the block
-    ErrorResult error;
-    SelectionRefPtr()->Collapse(RawRangeBoundary(newBlock, 0), error);
-    if (NS_WARN_IF(error.Failed())) {
-      return error.StealNSResult();
-    }
-  }
-
+  nsDependentAtomString tagName(&aTagName);
+  EditSubActionInfo subActionInfo(EditSubAction::eCreateOrRemoveBlock);
+  subActionInfo.blockType = &tagName;
   rv = rules->DidDoAction(subActionInfo, rv);
   if (NS_WARN_IF(NS_FAILED(rv))) {
     return rv;
diff --git a/editor/libeditor/HTMLEditor.h b/editor/libeditor/HTMLEditor.h
index 5cdc89ea26cf..01087be45b44 100644
--- a/editor/libeditor/HTMLEditor.h
+++ b/editor/libeditor/HTMLEditor.h
@@ -1108,6 +1108,17 @@ class HTMLEditor final : public TextEditor,
   MOZ_CAN_RUN_SCRIPT MOZ_MUST_USE nsresult OnModifyDocument();
 
  protected:  // edit sub-action handler
+  /**
+   * CanHandleHTMLEditSubAction() checks whether there is at least one
+   * selection range or not, and whether the first range is editable.
+   * If it's not editable, `Canceled()` of the result returns true.
+   * If `Selection` is in odd situation, returns an error.
+   *
+   * XXX I think that `IsSelectionEditable()` is better name, but it's already
+   *     in `EditorBase`...
+   */
+  EditActionResult CanHandleHTMLEditSubAction() const;
+
   /**
    * Called before inserting something into the editor.
    * This method may removes mPaddingBRElementForEmptyEditor if there is.
@@ -1696,8 +1707,9 @@ class HTMLEditor final : public TextEditor,
       nsTArray<OwningNonNull<nsINode>>& aNodeArray, nsAtom& aBlockTag);
 
   /**
-   * FormatBlockContainer() is implementation of "formatBlock" command of
-   * `Document.execCommand()`.  This applies block style or removes it.
+   * FormatBlockContainerWithTransaction() is implementation of "formatBlock"
+   * command of `Document.execCommand()`.  This applies block style or removes
+   * it.
    * NOTE: This creates AutoSelectionRestorer.  Therefore, even when this
    *       return NS_OK, editor may have been destroyed.
    *
@@ -1711,7 +1723,7 @@ class HTMLEditor final : public TextEditor,
    *                            called.
    */
   MOZ_CAN_RUN_SCRIPT MOZ_MUST_USE nsresult
-  FormatBlockContainer(nsAtom& aBlockType);
+  FormatBlockContainerWithTransaction(nsAtom& aBlockType);
 
   /**
    * InsertBRElementIfHardLineIsEmptyAndEndsWithBlockBoundary() determines if
@@ -2855,14 +2867,14 @@ class HTMLEditor final : public TextEditor,
   nsresult MakeDefinitionListItemWithTransaction(nsAtom& aTagName);
 
   /**
-   * InsertBasicBlockWithTransaction() inserts a block element whose name
-   * is aTagName at selection.
+   * FormatBlockContainerAsSubAction() inserts a block element whose name
+   * is aTagName at selection.  If selection is not collapsed and aTagName is
+   * nsGkAtoms::normal or nsGkAtoms::_empty, this removes block containers.
    *
    * @param aTagName            A block level element name.  Must NOT be
    *                            nsGkAtoms::dt nor nsGkAtoms::dd.
    */
-  MOZ_CAN_RUN_SCRIPT
-  nsresult InsertBasicBlockWithTransaction(nsAtom& aTagName);
+  MOZ_CAN_RUN_SCRIPT nsresult FormatBlockContainerAsSubAction(nsAtom& aTagName);
 
   /**
    * Increase/decrease the font size of selection.