Why is Kirupa forum so much nicer than other forums?

I’ve found Kirupa Forums to be a little unusual. I’ve never seen a single flamming. I’ve never seen any rudeness or unkindness. I’ve never seen any sort of spamming or indecent conduct.

How did this happen? Is it just that Kirupa forum has relatively good members, or is it some sort of account deletion policy that Kirupa has?