Unread posts should be marked somehow - a simple unread somewhere would be enough.
Another thing about unread posts - let's say first unread post is on page 3, and there is also page 4 (those users get really spammy sometimes ;) ). If I leave the topic before reading that fourth page, all posts are marked as read - even though I haven't chance to see the posts on page 4. Yet again (as I said about sections) - I have "mark as read" to mark topic completely read. I don't want this automatically. I want undisplayed posts to remain unread.