Taking this idea further, maybe part of the problem is that platforms reduce the quality metric for posts down to effectively a single dimension: upvotes / likes / thumbs up.

What if there were separate dimensions for: Factually accurate, Morally agreeable, and Polite?

A machine learning algorithm could quickly work out which groups of users have different ideological positions, and which topics are likely to devolve into flame wars, so it could require that users have a minimum politeness score to be able to participate in a debate.

It could also, as you say, check for echo chambers forming and incentivise people with differing opinions to enter a discussion to balance it out.