No...like y'know... you visit a link, but its indicator still has that yellowish color (on the forum page) like it hasn't been visited yet, that's all...
This has happened to me intermittently as well. Usually, unvisited posts or forums are highlighted 'till you visit them, and then
not highlighted until someone else posts a new reply.
What I've noticed is that sometimes all the posts or threads are highlighted even you've just been there and sometimes not. I haven't watched this carefully enough to say with certainty exactly what the pattern is but whatever is going on is not consistent on my end.