I'm used to seeing threads with posts I haven't read show up in bold, with checkmarks to the left.
I used to be able to click the checkbox, read what's new, hit the back button , and hit 'reload' and the thread (or threads) would lose the check box and the bold.
Lately, on the majority of threads (9 out of 10 - a guess,) I can read all th posts, reload several times, even log out and come in fro the main page again, and the thread is still bold with the checkmark. If I click the checkmark I am taken to the exact same spot in the thread as last time, and there are no new posts to read.
It's not the end of the world, but this feature did help me keep track of what threads had things I hadn't read in them when it was working.