Brad,

 

You may be right!  Naturally, it is difficult to test since when you mark all read, there aren't any new ones to test it with.  Then of course, you forget.  This time I stuck up a post-it, marked all read in just one section and came back later.  That section went to first post, the others to first unread.

 

Now, does that help you fix it?

 

\bob