Sure, simply mark the forums you want as favourite and unmark ones you don't want. A manual and tedious process, yes, but that's the one thing you can do.
The only so-called "syncing" that's ever been going on is that a long while ago a forum was marked as favourite when you bought the game it belonged to, but that has since stopped and I honestly haven't bothered to check if it's started working again. There was never anything going on after-the-fact.
Of course, you could also write a userscript to help solve the same issue a lot easier for others in the future, but I don't know of anyone who's already done so.
Post edited November 23, 2015 by Maighstir