'Mark forums read' vs. new messages that arrive just before we click it

Gentlemen, allow us to discuss the dangers of 'Mark forums read'.

We read everything we want to then we go to the Board Index
and click 'Mark forums read'.

But what if during those vital seconds while we are fumbling with our mouse an important message arrives?

Then it gets marked as read and we will never know about it!

Therefore we see 'Mark forums read' is never entirely safe!

If it actually acts different then there should be a mouseover saying
how.