Have you ever used Facebook? It’s much worse and this is specifically in reference to media that are against Facebook’s guidelines (e.g. nudity, gore, etc), not all content as a whole. Users doing some moderating in this context would simply be presenting flagged media randomly to users and asking if it breaks the guidelines.

Very completely different things. Subreddits would be the equivalent of Facebook Pages and they already have moderation tools for those that run the page.

Reddit is a bit different than what was suggested here, since moderators are not a rotating position there and this encourages power trips.

Stack overflow has the users do the moderation and it works well, maybe not perfect but its not bad.