I wonder how difficult it would be to implement some sort of labeling in the forums to mark threads which you would like to return to (similar to the starring ability of gmail, though the user defined labeling of gmail would be neat, but seems excessive) or to note a thread as SPAM for those threads which have reasonable titles but at some point deteriorated to SPAM so that forum users can avoid or follow the threads accordingly.

Not sure if that would cause too much clutter or anything, but just an idea I had after seeing some threads on AT.