This is one of my biggest pet peeves on this board. Has been ever since I joined. It's why I often won't get involved in threads that go beyond 2-3 pages if I wasn't there from the beginning.
It's especially frustrating when you get monster threads like the MW one. The same conversations have been had multiple times by people intelligently following along, and then you get some imbecile who jumps in with a herp derp take about some BS we've already all decided was wrong 10 pages ago.
This might be an abuse of moderator powers, but I've often thought of photshopping a dunce cap onto people's avatars when they do dumb s#!t like that.