           $set: root: root ? child  ## actually must be root
         ,
           multi: true
+        _noLongerRoot child if root?
       _submessagesChanged cmsg.root     ## old root
       _submessagesChanged root ? child  ## new root
     doc =

      parent: parent
      position: position
      oldParent: oldParent
    if importing
      #cmsg = Messages.findOne child
      doc.updator = cmsg.creator

    root = null
  if canEdit(child) and canPost group, parent
    cmsg = Messages.findOne child
    oldIndex = null
    if oldParent
      oldParent = findMessageParent child
      if oldParent?
        oldIndex = oldParent.children.indexOf child
        Messages.update oldParent._id,
          $pop: children: child
    if parent?
