Say I go to my User CP (on let's say PC 1), and a thread (let's call it Thread 1) is bold indicating there are new unread posts in it. I click the 'go to first new post button' and the pages takes me to the first new unread post and I read all remaining posts. Go back to CP and post is un bold.
Now I go on to PC 2 later in the day. Pull up my User CP and it will have Thread 1 in bold again, whether or not there's a new post or not since I last viewed it on PC 1. Click on 'first unread post' and it takes me to the same post as earlier in the day on PC1 took me to. At this point all I can do to see if something has a new post is look at the time of last post and try to match it up with when I think what time it was I was last on PC 1.
Now on to the next day it seems to reset itself and all the bold threads are ones which truly do have new posts unread by the user. Any combination of computer or browser will yield the same results. Other forums seem to update in real-time in relation to the user, not by locale.
Is there any way to make it update more realistically instead of per computer per day...? I have some of my own unprofessional ideas of what's happening, but I'll just let the experts chime in. Maybe it's to help save resources on the server, I dunno.