Not sure if there is a setting, but often when I read a thread it would mark the entire sub-forum threads as read. Such as just now there was 2 unread thread “Burton Customs” and “New Technology” in the Binding Sub-forum. When I finished reading the “Burton Customs” thread it marked the entire sub-forum as read and thus I no longer have the “last unread” button for “New Technologies” I assumed it is the forums default behavior and tried to find a setting to prevent this behavior in the User CP to no avail.

további részletek:
How to prevent entire forum from being marked read?