I had a not similar but related idea, basically borne from my hatred of Twitter. Basically, you'd only be able to make a comment if you have a credit. Credits would be time based, probably 1 or 2 a day. The only other way to get credits is if the person you replied to likes your comment. Basically, the idea being to quit getting people being so controversial and argumentative.
Edit:
I kept replying below describing some vision that doesn't exist, which I feel is rude to the OP and Minus, so I'll not reply further. As I have little intention in building anything at the moment, feel free to take anything you like from it, Minus et al.