They do warn you about scammers, and my feeling is that if they tried to filter out the vermin who say "my agent will arrive with a cashier's check to pick it up" the scammers would just find some way around it, and people would get a false sense of security to boot. Whack-a-mole games, in other words.
A site for discussion would be Discogs, where I've had almost nothing but great experiences: all nice, honest people. Maybe the fix for Craigslist would be to split into verticals, where a community could develop, something that's absent now.
What I don’t like is the emotional energy it takes to filter them out.
Feels like the time is ripe for something like that, too. I think you're right, that would really up Craigslist's game.