When I go to a particular forum threads have remained highlighted as unread, even after I've left the site for a period of 12 hours or so. For instance the movie forum has posts marked as unread dating back to January 7th, it appears like there are 4 pages of new posts since I last visited. I've been on and off the site dozens of times since then. This has never happened to me in 10 years on this board. Any advice?

I used the forum tool "mark forum read" for this reason. Seems they may have changed a setting so that unless you open something it stays as unread now...

It's a temporary result of this forum update. Once you mark the forums read for the first time (which you need to do on your computer or load the full version of the forum on your phone), that'll clear out the backlog. From that point on, only threads with unread posts will be in bold.

Yes, it has been changed. It used to time out too quickly, so you would get things marked as read before you were done browsing the forum.

There was a side effect of this change that made threads show as unread which had posts in the last couple of weeks, or so.

As jpcamb said, you can 'Mark Forums Read' which is found under the Quick Links menu at the top of the page.

This has been fully discussed in the main feedback thread on the changes.

Yeah I guess I should have checked the feedback thread. Oh well, thanks all.