Message threads are arranged by date of the most recent activity, with the newest appearing on top. "Activity" consists of any additions or modifications to articles within the thread. So anytime a new reply is posted or one is modified, the thread will be bumped to the top of the list.
If a thread gets bumped to the top but does not appear to have changed, one of three things may have happened: (1) A new reply was posted but then deleted shortly thereafter, (2) A new reply has been posted by a non-user, and is currently in the queue for review by an admin (and therefore not yet visible), or (3) The message was bumped by an administrator.
I sometimes bump old topics, either if they've been featured in a recent newsletter, or if a question has gone unanswered and looks like it needs some help with a refresh. In the case of this article, however, it was bumped by a reply from a non-user, and so wasn't yet visible. But it is now.
Regards,
Jonathan Akinson
www.ballroomdancers.com