I think you’re overestimating how much moderation it takes to keep a community whole. HN is dang and a handful of other moderators and things are stable. If you could have AI even approach 90% of that then it will truly solve problems.
Also, LLM aren't unbiased, all data it trains on is biased one way or another. Ask any HR question and see for yourself how its answers lean to be HR BS that favours employers.