When you're visiting the forum index page(f. ex: http://hack3r.com/forum), you aren't notified of new posts inside a forum topic.
I don't bother opening a forum topic when I don't think there are any new posts.

When you go inside a forum topic, or at the index page of a forum topic(f. ex: http://hack3r.com/forums/bugs), it will tell you there are new posts but why not before? I bet a lot of people are the same as me and assume no new posts have been made.