--- a/editor/libeditor/HTMLEditRules.cpp
+++ b/editor/libeditor/HTMLEditRules.cpp
@@ -6740,41 +6740,43 @@ HTMLEditRules::ReturnInParagraph(Selecti
 
   int32_t offset;
   nsCOMPtr<nsINode> parent = EditorBase::GetNodeLocation(node, &offset);
 
   bool doesCRCreateNewP = htmlEditor->GetReturnInParagraphCreatesNewParagraph();
 
   bool newBRneeded = false;
   bool newSelNode = false;
-  nsCOMPtr<nsIContent> sibling;
+  nsCOMPtr<nsIContent> brNode;
   nsCOMPtr<nsIDOMNode> selNode = GetAsDOMNode(aNode);
   int32_t selOffset = aOffset;
 
   if (aNode == aPara && doesCRCreateNewP) {
     // we are at the edges of the block, newBRneeded not needed!
-    sibling = node->AsContent();
+    brNode = nullptr;
   } else if (EditorBase::IsTextNode(aNode)) {
     // at beginning of text node?
     if (!aOffset) {
       // is there a BR prior to it?
-      sibling = htmlEditor->GetPriorHTMLSibling(node);
-      if (!sibling ||
-          !htmlEditor->IsVisibleBRElement(sibling) ||
-          TextEditUtils::HasMozAttr(GetAsDOMNode(sibling))) {
+      brNode = htmlEditor->GetPriorHTMLSibling(node);
+      if (!brNode ||
+          !htmlEditor->IsVisibleBRElement(brNode) ||
+          TextEditUtils::HasMozAttr(GetAsDOMNode(brNode))) {
         newBRneeded = true;
+        brNode = nullptr;
       }
     } else if (aOffset == static_cast<int32_t>(node->Length())) {
       // we're at the end of text node...
       // is there a BR after to it?
-      sibling = htmlEditor->GetNextHTMLSibling(node);
-      if (!sibling ||
-          !htmlEditor->IsVisibleBRElement(sibling) ||
-          TextEditUtils::HasMozAttr(GetAsDOMNode(sibling))) {
+      brNode = htmlEditor->GetNextHTMLSibling(node);
+      if (!brNode ||
+          !htmlEditor->IsVisibleBRElement(brNode) ||
+          TextEditUtils::HasMozAttr(GetAsDOMNode(brNode))) {
         newBRneeded = true;
+        brNode = nullptr;
         offset++;
       }
     } else {
       if (doesCRCreateNewP) {
         nsCOMPtr<nsIDOMNode> tmp;
         nsresult rv =
           htmlEditor->SplitNode(selNode, aOffset, getter_AddRefs(tmp));
         if (NS_WARN_IF(NS_FAILED(rv))) {
@@ -6801,61 +6803,57 @@ HTMLEditRules::ReturnInParagraph(Selecti
       if (!nearNode || !htmlEditor->IsVisibleBRElement(nearNode) ||
           TextEditUtils::HasMozAttr(GetAsDOMNode(nearNode))) {
         newBRneeded = true;
         parent = node;
         offset = aOffset;
         newSelNode = true;
       }
     }
-    if (!newBRneeded) {
-      sibling = nearNode;
+    if (!newBRneeded && TextEditUtils::IsBreak(nearNode)) {
+      brNode = nearNode;
     }
   }
   if (newBRneeded) {
     // Don't modify the DOM tree if mHTMLEditor disappeared.
     if (NS_WARN_IF(!mHTMLEditor)) {
       return EditActionResult(NS_ERROR_NOT_AVAILABLE);
     }
 
     // if CR does not create a new P, default to BR creation
     if (NS_WARN_IF(!doesCRCreateNewP)) {
       return EditActionResult(NS_OK);
     }
 
-    sibling = htmlEditor->CreateBR(parent, offset);
+    brNode = htmlEditor->CreateBR(parent, offset);
     if (newSelNode) {
       // We split the parent after the br we've just inserted.
       selNode = GetAsDOMNode(parent);
       selOffset = offset + 1;
     }
   }
   EditActionResult result(
-    SplitParagraph(GetAsDOMNode(aPara), sibling, aSelection,
+    SplitParagraph(GetAsDOMNode(aPara), brNode, aSelection,
                    address_of(selNode), &selOffset));
   result.MarkAsHandled();
   if (NS_WARN_IF(result.Failed())) {
     return result;
   }
   return result;
 }
 
-/**
- * SplitParagraph() splits a paragraph at selection point, possibly deleting a
- * br.
- */
 nsresult
 HTMLEditRules::SplitParagraph(nsIDOMNode *aPara,
                               nsIContent* aBRNode,
                               Selection* aSelection,
                               nsCOMPtr<nsIDOMNode>* aSelNode,
                               int32_t* aOffset)
 {
   nsCOMPtr<Element> para = do_QueryInterface(aPara);
-  NS_ENSURE_TRUE(para && aBRNode && aSelNode && *aSelNode && aOffset &&
+  NS_ENSURE_TRUE(para && aSelNode && *aSelNode && aOffset &&
                  aSelection, NS_ERROR_NULL_POINTER);
 
   // split para
   // get ws code to adjust any ws
   nsCOMPtr<nsIContent> leftPara, rightPara;
   NS_ENSURE_STATE(mHTMLEditor);
   nsCOMPtr<nsINode> selNode(do_QueryInterface(*aSelNode));
   nsresult rv =
@@ -6873,17 +6871,18 @@ HTMLEditRules::SplitParagraph(nsIDOMNode
                                HTMLEditor::EmptyContainers::yes,
                                getter_AddRefs(leftPara),
                                getter_AddRefs(rightPara));
   if (NS_WARN_IF(offset == -1)) {
     return NS_ERROR_FAILURE;
   }
   // get rid of the break, if it is visible (otherwise it may be needed to prevent an empty p)
   NS_ENSURE_STATE(mHTMLEditor);
-  if (mHTMLEditor->IsVisibleBRElement(aBRNode)) {
+  if (aBRNode &&
+      mHTMLEditor->IsVisibleBRElement(aBRNode)) {
     NS_ENSURE_STATE(mHTMLEditor);
     rv = mHTMLEditor->DeleteNode(aBRNode);
     NS_ENSURE_SUCCESS(rv, rv);
   }
 
   // remove ID attribute on the paragraph we just created
   RefPtr<Element> rightElt = rightPara->AsElement();
   NS_ENSURE_STATE(mHTMLEditor);

--- a/editor/libeditor/HTMLEditRules.h
+++ b/editor/libeditor/HTMLEditRules.h
@@ -292,21 +292,39 @@ protected:
                        Tables aTables = Tables::yes);
   Element* IsInListItem(nsINode* aNode);
   nsAtom& DefaultParagraphSeparator();
   nsresult ReturnInHeader(Selection& aSelection, Element& aHeader,
                           nsINode& aNode, int32_t aOffset);
   EditActionResult ReturnInParagraph(Selection* aSelection, nsINode* aHeader,
                                      nsINode* aTextNode, int32_t aOffset,
                                      nsIContent* aChildAtOffset);
+
+  /**
+   * SplitParagraph() splits the parent block, aPara, at aSelNode - aOffset.
+   *
+   * @param aPara       The parent block to be split.
+   * @param aBRNode     Next <br> node if there is.  Otherwise, nullptr.
+   *                    If this is not nullptr, the <br> node may be removed.
+   * @param aSelection  The selection.
+   * @param aSelNode    Set the selection container to split aPara at.
+   *                    Actual container node will be set by this method.
+   *                    XXX: The only caller ReturnInParagraph() doesn't need
+   *                         this result.
+   * @param aOffset     Set the offset in the container.
+   *                    Actual offset will be set by this method.
+   *                    XXX: The only caller ReturnInParagraph() doesn't need
+   *                         this result.
+   */
   nsresult SplitParagraph(nsIDOMNode* aPara,
                           nsIContent* aBRNode,
                           Selection* aSelection,
                           nsCOMPtr<nsIDOMNode>* aSelNode,
                           int32_t* aOffset);
+
   nsresult ReturnInListItem(Selection& aSelection, Element& aHeader,
                             nsINode& aNode, int32_t aOffset);
   nsresult AfterEditInner(EditAction action,
                           nsIEditor::EDirection aDirection);
   nsresult RemovePartOfBlock(Element& aBlock, nsIContent& aStartChild,
                              nsIContent& aEndChild);
   void SplitBlock(Element& aBlock,
                   nsIContent& aStartChild,