Avoid creating new thread root+<hr> when they already exist.

src/Filtering/ThreadHiding.coffee

@@ -16,10 +16,8 @@ ThreadHiding =
     $.prepend @OP.nodes.root, ThreadHiding.makeButton @, 'hide'
 
   onrefresh: ->
-    for threadID, thread of g.BOARD.threads when thread.isHidden
+    for threadID, thread of g.BOARD.threads when thread.isHidden and thread.stub
-      hasStub = !!thread.stub
+      $.prepend thread.OP.nodes.root.parentNode, thread.stub
-      ThreadHiding.show thread
-      ThreadHiding.hide thread, hasStub
     return
 
   syncCatalog: ->

src/General/Build.coffee

@@ -271,6 +271,16 @@ Build =
   thread: (board, data) ->
     Build.spoilerRange[board] = data.custom_spoiler
 
+    if (OP = board.posts[data.no]) and parent = OP.nodes.root.parentNode
+      root = parent
+      hr   = parent.nextElementSibling
+      $.rmAll root
+    else
+      root = $.el 'div',
+        className: 'thread'
+        id: "t#{data.no}"
+      hr   = $.el 'hr'
+
     nodes = []
     for obj in [data].concat data.last_replies or []
       nodes.push if post = board.posts[obj.no]
@@ -282,8 +292,5 @@ Build =
     if data.omitted_posts
       nodes.splice 1, 0, Build.summary board.ID, data.no, data.omitted_posts, data.omitted_images
 
-    root = $.el 'div',
-      className: 'thread'
-      id: "t#{data.no}"
     $.add root, nodes
-    root
+    [root, hr]

src/General/Index.coffee

@@ -188,8 +188,8 @@ Index =
     threads     = []
     posts       = []
     for threadData in Index.liveThreadData
-      threadRoot = Build.thread g.BOARD, threadData
+      [threadRoot, hr] = Build.thread g.BOARD, threadData
-      Index.nodes.push threadRoot, $.el 'hr'
+      Index.nodes.push threadRoot, hr
       if thread = g.BOARD.threads[threadData.no]
         thread.setStatus 'Sticky', !!threadData.sticky
         thread.setStatus 'Closed', !!threadData.closed
@@ -250,6 +250,6 @@ Index =
       nodes = Index.sortedNodes[nodesPerPage * pageNum ... nodesPerPage * (pageNum + 1)]
     else
       nodes = Index.sortedNodes
-    $.event 'IndexRefresh'
     $.rmAll Index.root
+    $.event 'IndexRefresh'
     $.add Index.root, nodes