It would show the "new" when someone edits a post, I have seen that personally so it's not that, and even if it did I checked ALL threads in AeF forum and noone edited something there since the last time I visited.
I made some screens to better showcase this.
Here it shows me that there should be something new.
So I click on it...
Nothing found so I check the forum itself...
WTF?! WHY? And this happens ALL the time on all clan boards I always need to manually press "mark all as read".
I sometimes miss new posts because of this since 99% there is not something new and I automatically press mark as read.