I have been reading every page in every thread since this morning early, and yet it keeps going back to 9:35 this morning as if I've read no posts since then.
This is not a feature issue, it is a break.
It's a feature issue. the performance thread is strictly for performance issues - aka, does the site load quickly, or slowly? That's pretty much all it's for.
As for your problem, try hitting "mark all messages read" and report back. I might suggest hitting "all unread topics" first.