>Why exactly is it that such a large portion of the discussion here tends toward actual adult conversation?
I attribute it to a few things that work in synergy
1. The voting model, and structure of the site work well for the crowd that gathers here. Keeping spam away is automated enough to keep the signal to noise high.
2. Dang keeps us from doing stupid things consistently enough that we collectively have learned good manners.
3. We've all seen how quickly things can get swamped, to make us really appreciative of what we've got here, and more careful about doing stupid things.
4. Upvoting, etc. are paced such that you don't get access to a bit of power until you understand it. It's subtle enough but very effective.
5. The management is not driven to push "engagement" or "stickiness" by the need to sell advertising.
If you took the codebase and started again, I'm not sure it would work more than 5% of the time.