I've thought a bit about this recently, since HN and Reddit in particular are prone to have the posts sorted by how much it appeals to the average user.

Other systems such as Twitter and Facebook limit you extremely in the fact that you only converse with likeminded people, and when you don't, you'll most likely never end up in a constructive discussion, just in a flamewar since everyone is dead set on their opinion already, and because of the limitations in the commentning system discourages it.

What about a system based on NLP / ML where users can flag the truthfulness or speculation? (For the UI part, I'm thinking something similar to Medium, where you can select a favorite passage from a blog-post)

If you rank posts by how objectively true they are, and the amount of truth/false-votes they get, you should be able to bootstrap posts in, while also dynamically adjust to the popularity of it (number of votes received).

I know this is still a stretch with current machine learning technology, but I think we (the internet) really need a place where we can more easily filter out the bullshit, and discuss the things that really matter with people who don't already agree.