diff --git a/editor/libeditor/HTMLEditSubActionHandler.cpp b/editor/libeditor/HTMLEditSubActionHandler.cpp
index 0afcb21890d8d..0925406d2d4c5 100644
--- a/editor/libeditor/HTMLEditSubActionHandler.cpp
+++ b/editor/libeditor/HTMLEditSubActionHandler.cpp
@@ -12736,21 +12736,44 @@ NS_ERROR_FAILURE
 )
 ;
 }
-EditActionResult
-result
-=
-HandleDeleteCollapsedSelectionAtCurrentBlockBoundary
+AutoBlockElementsJoiner
+joiner
+;
+if
 (
-aDirectionAndAmount
-MOZ_KnownLive
+!
+joiner
+.
+PrepareToDeleteCollapsedSelectionAtCurrentBlockBoundary
 (
 *
+this
+aDirectionAndAmount
+*
 scanFromStartPointResult
 .
 ElementPtr
 (
 )
+startPoint
+)
+)
+{
+return
+EditActionCanceled
+(
 )
+;
+}
+EditActionResult
+result
+=
+joiner
+.
+Run
+(
+*
+this
 startPoint
 )
 ;
@@ -12765,12 +12788,20 @@ Succeeded
 HTMLEditor
 :
 :
-HandleDeleteCollapsedSelectionAtCurrentBlockBoundary
+AutoBlockElementsJoiner
+:
+:
+Run
 (
 )
+failed
 "
 "
-failed
+(
+current
+block
+boundary
+)
 "
 )
 ;
@@ -15547,12 +15578,19 @@ return
 result
 ;
 }
-EditActionResult
+bool
 HTMLEditor
 :
 :
-HandleDeleteCollapsedSelectionAtCurrentBlockBoundary
+AutoBlockElementsJoiner
+:
+:
+PrepareToDeleteCollapsedSelectionAtCurrentBlockBoundary
 (
+const
+HTMLEditor
+&
+aHTMLEditor
 nsIEditor
 :
 :
@@ -15569,11 +15607,20 @@ aCaretPoint
 {
 MOZ_ASSERT
 (
+aHTMLEditor
+.
 IsEditActionDataAvailable
 (
 )
 )
 ;
+mMode
+=
+Mode
+:
+:
+JoinCurrentBlock
+;
 if
 (
 HTMLEditUtils
@@ -15587,18 +15634,9 @@ aCurrentBlockElement
 )
 {
 return
-EditActionCanceled
-(
-)
+false
 ;
 }
-nsCOMPtr
-<
-nsINode
->
-leftNode
-rightNode
-;
 if
 (
 aDirectionAndAmount
@@ -15610,36 +15648,40 @@ nsIEditor
 ePrevious
 )
 {
-leftNode
+mLeftContent
 =
+aHTMLEditor
+.
 GetPreviousEditableHTMLNode
 (
 aCurrentBlockElement
 )
 ;
-rightNode
+mRightContent
 =
 aCaretPoint
 .
-GetContainer
+GetContainerAsContent
 (
 )
 ;
 }
 else
 {
-rightNode
+mRightContent
 =
+aHTMLEditor
+.
 GetNextEditableHTMLNode
 (
 aCurrentBlockElement
 )
 ;
-leftNode
+mLeftContent
 =
 aCaretPoint
 .
-GetContainer
+GetContainerAsContent
 (
 )
 ;
@@ -15647,39 +15689,59 @@ GetContainer
 if
 (
 !
-leftNode
+mLeftContent
 |
 |
 !
-rightNode
+mRightContent
 )
 {
 return
-EditActionCanceled
-(
-)
+false
 ;
 }
-if
-(
+return
+!
 HTMLEditor
 :
 :
 NodesInDifferentTableElements
 (
 *
-leftNode
+mLeftContent
 *
-rightNode
+mRightContent
 )
+;
+}
+EditActionResult
+HTMLEditor
+:
+:
+AutoBlockElementsJoiner
+:
+:
+HandleDeleteCollapsedSelectionAtCurrentBlockBoundary
+(
+HTMLEditor
+&
+aHTMLEditor
+const
+EditorDOMPoint
+&
+aCaretPoint
 )
 {
-return
-EditActionCanceled
+MOZ_ASSERT
 (
+mLeftContent
+)
+;
+MOZ_ASSERT
+(
+mRightContent
 )
 ;
-}
 EditActionResult
 result
 (
@@ -15696,6 +15758,8 @@ aCaretPoint
 AutoTrackDOMPoint
 tracker
 (
+aHTMLEditor
+.
 RangeUpdaterRef
 (
 )
@@ -15703,63 +15767,22 @@ RangeUpdaterRef
 pointToPutCaret
 )
 ;
-if
-(
-NS_WARN_IF
-(
-!
-leftNode
--
->
-IsContent
-(
-)
-)
-|
-|
-NS_WARN_IF
-(
-!
-rightNode
--
->
-IsContent
-(
-)
-)
-)
-{
-return
-EditActionResult
-(
-NS_ERROR_FAILURE
-)
-;
-}
 result
 |
 =
+aHTMLEditor
+.
 TryToJoinBlocksWithTransaction
 (
 MOZ_KnownLive
 (
 *
-leftNode
--
->
-AsContent
-(
-)
+mLeftContent
 )
 MOZ_KnownLive
 (
 *
-rightNode
--
->
-AsContent
-(
-)
+mRightContent
 )
 )
 ;
@@ -15799,6 +15822,8 @@ result
 nsresult
 rv
 =
+aHTMLEditor
+.
 CollapseSelectionTo
 (
 pointToPutCaret
diff --git a/editor/libeditor/HTMLEditor.h b/editor/libeditor/HTMLEditor.h
index 390523503a386..8aa15f219aa38 100644
--- a/editor/libeditor/HTMLEditor.h
+++ b/editor/libeditor/HTMLEditor.h
@@ -5474,6 +5474,34 @@ WSRunScanner
 aWSRunScannerAtCaret
 )
 ;
+class
+MOZ_STACK_CLASS
+AutoBlockElementsJoiner
+final
+{
+public
+:
+bool
+PrepareToDeleteCollapsedSelectionAtCurrentBlockBoundary
+(
+const
+HTMLEditor
+&
+aHTMLEditor
+nsIEditor
+:
+:
+EDirection
+aDirectionAndAmount
+Element
+&
+aCurrentBlockElement
+const
+EditorDOMPoint
+&
+aCaretPoint
+)
+;
 [
 [
 nodiscard
@@ -5481,30 +5509,131 @@ nodiscard
 ]
 MOZ_CAN_RUN_SCRIPT
 EditActionResult
-HandleDeleteCollapsedSelectionAtOtherBlockBoundary
+Run
 (
-nsIEditor
+HTMLEditor
+&
+aHTMLEditor
+const
+EditorDOMPoint
+&
+aCaretPoint
+)
+{
+switch
+(
+mMode
+)
+{
+case
+Mode
 :
 :
-EDirection
-aDirectionAndAmount
-nsIEditor
+JoinCurrentBlock
+:
+{
+EditActionResult
+result
+=
+HandleDeleteCollapsedSelectionAtCurrentBlockBoundary
+(
+aHTMLEditor
+aCaretPoint
+)
+;
+NS_WARNING_ASSERTION
+(
+result
+.
+Succeeded
+(
+)
+"
+AutoBlockElementsJoiner
 :
 :
-EStripWrappers
-aStripWrappers
-Element
+"
+"
+HandleDeleteCollapsedSelectionAtCurrentBlockBoundary
+(
+)
+failed
+"
+)
+;
+return
+result
+;
+}
+case
+Mode
+:
+:
+NotInitialized
+:
+return
+EditActionIgnored
+(
+)
+;
+}
+return
+EditActionResult
+(
+NS_ERROR_NOT_INITIALIZED
+)
+;
+}
+private
+:
+[
+[
+nodiscard
+]
+]
+MOZ_CAN_RUN_SCRIPT
+EditActionResult
+HandleDeleteCollapsedSelectionAtCurrentBlockBoundary
+(
+HTMLEditor
 &
-aOtherBlockElement
+aHTMLEditor
 const
 EditorDOMPoint
 &
 aCaretPoint
-WSRunScanner
-&
-aWSRunScannerAtCaret
 )
 ;
+enum
+class
+Mode
+{
+NotInitialized
+JoinCurrentBlock
+}
+;
+nsCOMPtr
+<
+nsIContent
+>
+mLeftContent
+;
+nsCOMPtr
+<
+nsIContent
+>
+mRightContent
+;
+Mode
+mMode
+=
+Mode
+:
+:
+NotInitialized
+;
+}
+;
 [
 [
 nodiscard
@@ -5512,20 +5641,28 @@ nodiscard
 ]
 MOZ_CAN_RUN_SCRIPT
 EditActionResult
-HandleDeleteCollapsedSelectionAtCurrentBlockBoundary
+HandleDeleteCollapsedSelectionAtOtherBlockBoundary
 (
 nsIEditor
 :
 :
 EDirection
 aDirectionAndAmount
+nsIEditor
+:
+:
+EStripWrappers
+aStripWrappers
 Element
 &
-aCurrentBlockElement
+aOtherBlockElement
 const
 EditorDOMPoint
 &
 aCaretPoint
+WSRunScanner
+&
+aWSRunScannerAtCaret
 )
 ;
 [