[Lucid:]

I also have a compulsion to never leave forums unread. I don't know what I'll do when we start getting more people posting more threads all the time. @.@

I've noticed that if you read a thread in a subforum then go straight to the main page, it will say there are unread threads in that subforum when there aren't. going to the subforum page makes it show up as read.
Same thing happens in a thread. if I post in a thread, even if that thread was previously registered as read, and then go straight to the main page, it says that the subforum I just posted in is unread, even though everything was read and I hopefully know what I just posted.

if I am online and sit looking at the main or subforum page too long without any activity (which happens to me a lot because I get distracted by other stuff), everything decides to get marked as unread. so I have to pay attention to the "last post" section.

I think I basically said what Fenris just did but with more words. =P

I always thought it was just a little quirk in the forum, and I didn't mind the extra one or two clicks to get everything marked as read. but if it can be fixed, that would be wonderful. 8D