Guest,
The only poster that I know, who meets your criteria is Malcolm Douglas.
He hasn't left, but continues to ignore the the stuff that doesn't interest him, and posts intelligent and informed stuff when he has something to say.
Personally, I don't engage in the threads that you mention, prefering to offer help when I can, or ask for help when I'm sure someone will be able to offer advice.
Do you stop drinking somewhere because a few people at the next table talk crap?
Ed