   message.updators = authors
   diff = _.clone message
   for author in authors
-    message["authors." + escapeUser author] = now
+    message["authors.#{escapeUser author}"] = now
   Messages.update id,
     $set: message
   diff.id = id

      Messages.update
        root: child
      ,
        $set: root: root ? child  ## actually must be root
      ,
        multi: true
      EmojiMessages.update
        root: child
      ,
        $set: root: root ? child  ## actually must be root
      ,
        multi: true
      _noLongerRoot child if root?

  if parent?
    _messageAddChild child, parent, position
  if root != cmsg.root
    update = root: root
    if group != cmsg.group
      update.group = group
      ## First MessagesDiff has the initial group; add Diff if it changes.
      ## (Unclear whether we should track group at all, though.)
      now = new Date
      username = Meteor.user().username
      MessagesDiff.insert
        id: cmsg._id
        group: cmsg.group
        updated: now
        updators: [username]
      Messages.update child,
        $set: _.extend {"authors.#{escapeUser username}": now}, update
    else
      Messages.update child,
        $set: update
    EmojiMessages.update
      message: child
    ,
      $set: update
    ,
      multi: true
    if cmsg.root?
