I find it really bizarre that the main shoutbox page only tells me if there are new posts in the various forums, and does not also count posts with new comments. Maybe it was simpler to implement, but it makes the shoutbox a lot less convenient to visit regularly.
When I come back to the shoutbox the main thing I want to know is where is all the new stuff I have not yet looked at. I shouldn't have to click through all the forums because I can't remember if the last time I was there was morning or evening a couple days ago.
Ideally the "new" for each forum should include the new comments within it. If that is too expensive to compute on the website, then color the "most recent post" differently if it is more recent than the last visit? That would probably be enough.
Also, a new post with no comments should display "0 new" or something when you view a forum-- currently, you can see "new" things in the main shoutbox page, then view the forum and nothing looks new... but somewhere, one of the posts with no comments is quietly new and you don't know which one it is until you click them all.