Seems to be a recent regression for forum read tracking.

1. See a discussion like this: http://moodle.org/mod/forum/discuss.php?d=95260 (probably marked unread orange for you)

2. Reload the page, and the orange is gone as it should be (because it's now read).

3. Reply to the first post: http://moodle.org/mod/forum/post.php?reply=420698 (don't need to actually post anything, just look at the page)

Note all the replies are shown as unread (orange) now.

4. Going to http://moodle.org/mod/forum/discuss.php?d=95260 again show they are really correct in the db, so it's just the display on post.php ...