Well actually once you've read ALL the posts it does act that way in that it will once again take you to the first post
I think it's very intuitive and works properly. If you've never read any of the posts it does take you to the first unread, if you've read them then it takes you to the last UNREAD. Once all have been read it then goes back to the first post.
At least it sure seems to work that way.
