So, the question becomes how do we rank posts and comments in a way that is not based on either upvotes or down votes or number of comments? I could see a trust value being made for each user based on trusted users marking others as trusted combined with a personal trust score, but that puts a barrier on new users and enforces echo chambers.

What else could be tried?

It can still be used to artificially pump up an idea. Or used to bury one.