Its almost impossible to de-dumb-ass-afy any social network or comment section. How can you prevent the lowest common denominator on public forums from posting

Its almost impossible to de-dumb-ass-afy any social network or comment section. How can you prevent the lowest common denominator on public forums from posting heinous content / ignorant opinions? Moderators checking every post doesn't scale and AI may never understand nuance. One direction would be Hacker News' model of a more restrictive approach where new users must grind up their trust score in order to receive full citizenship.