Indizine flagged this one, and as soon as the penny dropped, I realised we had missed something major off the new forum 
When you look at a forum now, such as General Business Discussion, any threads that are bold mean you have either never visited this discussion before, or there have been new posts to the discussion since your last visit.
You already get this information in your forum profile, but it is visually quicker and easier to see it from the main forum. eg:
Threads not in bold mean there are no new posts since your last visit.
Threads in bold mean there are new posts since your last visit.
If you select a thread in bold, you will be taken to the first new post.
The first new post may be the first post of the thread if you haven't visited it before, or it may be 25 posts in, if you are involved in a discussion.
vBulletin forums and other forum software typically use an icon in the thread list to take you to the first new post. But we have done away with that, and combined it with the thread view.
We think it is less confusing doing it this way, rather than adding in a small icon into the thread view, but if the consensus says otherwise, we can revert to a vBulletin style icon in the future.
This functionality is only available to members who are logged in. Any guests will see all forum threads as "unread" (ie bold).
As we have moved to a new platform, we are unable to carry over views from the previous vBulletin forum. So threads and posts are only marked as read as from 28th March 2014.
Hope that makes sense 
