Thinking you're better than others because you're into LessWrong is no worse than thinking you're better than others because you're not into LessWrong!
I would say at least 1 in 5 posts that get more then 100 karma are solid enough to stand up to ~1 hour of careful scrutiny, even by a reasonably well informed amateur.
It's the EA forum where things are a bit looser.
Some communities have positive signal. Others have negative signal.