Another note about the unread-mark behavior...

Sometimes I will view the main page (the "top index") and it shows exactly 1 unread post within a specific thread, including the name of that thread. So I click directly on that thread name and it brings me to the single unread post within that thread. As expected.

But when I'm done reading that post, and I click the link to go up one level to that forum's index, I see that there's a thread about 12 items down in the list with five new/unread posts in it.

I click on that thread and I see that it's the five posts I already read 15 minutes ago.

My point is that there is often a discrepancy between the unread count shown on the main index page, and the unread count for a thread within the forum. And in the case cited above, the main index page was correct, it was the forum view that was showing (incorrectly) that I hadn't read those five posts in that thread.