User blog comment:Meighan/Wiki Wisdom: Reacting to Trolls and Vandalism/@comment-3441771-20111116082728/@comment-961279-20111124165100

If they are using the same IP address, you can leave a message on their talk page and they will be alterted to the next time they make an edit. No guarantees they'll read it, though. If the IP address changes, not much you can do to get to a message to them.