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…
The only people who haven't given up on the approach of a massive symbolic reasoning database to work out what's true and false are Cyc. https://en.wikipedia.org/wiki/Cyc
You might be able to have a system which auto-flags known bullshit statements, but people will get outraged by that.