To have ROI < 0 for all posts is not a bad idea at all.
This means people, only if they believe in the value of their posts will promote their posts.
For ROI>0 on value content, this would need someone to curate all the posts as value and non-value content.
Sometimes the border is very thin and bots,even humans can not do this.
The best is to comment it @themarkymark post. I am sure he will reply you back.
FD.
The best way to solve this is an instant bot, but everyone will just use the ones that do give them an ROI.
Yes, you cannot solve the problem alone. It's a tricky one. And probably it's not a technical issue, it's an human issue. It's like a war game: stakeholders must constantly act to promote quality and to avoid short term exploits of the platform.
That is correct...free market rules and game theory involved.