However as others have said a reputation system for participants is absolutely key. Any platform like this has to assume it is going to be flooded by bots trying to influence opinion on behalf of corporations, foreign governments and activists.
A reputation where users gain reputation slowly (through work, by verifying sources, etc..) become more able to influence opinion, but the reputation drops quickly if they are found to be misleading people. How this actually works is harder than it seems if you want a truly robust system.
When I think of platforms like this I think of Galileo[0]. He was perceived as a troll or heretic in his time, but of course he was right. How do you create a platform that allows correct ideas to flourish even when they go against conventional wisdom?