The forum thinks that if you log out, you have read all posts on the forum. So only post made after that are considered 'unread', and are displayed in bold. You can see when you last visited on the top left of the page, just below 'Welcome, .'
However, I have had a few times that suddenly all topics turned 'read' and the interface told me that I had last visited a few minutes ago. Somehow, the board seemed to think I had logged out. Perhaps you are refering to this?
I think it happens when I spend a long time in a certain topic, but I am not quite sure about that because it didn't happen when I stayed logged in and went down to have dinner.
EDIT: it happened twice today. Each time I was taking my time composing a long reply to a thread.
Bookmarks