Slashdot has a meta-moderation setup where random users (with at least a minimum tenure and rating on the site) would get to vote on the quality of the moderation for randomly selected posts. I still think that this has a lot of potential for improving moderation, even if it's just used as a way of ferriting out problematic moderation.
I don't understand why it never caught on elsewhere.
Meta-moderation was an interesting idea, though they seemed to have stopped promoting it much by the time I stopped posting there often. I’m not convinced it’s as effective as having a small pool of “super-moderators” who can not only affect the prioritisation/visibility but also comment themselves to guide contributors in positive directions, but practically speaking, it might be more scalable.