According to the statistics from 2018: a year in spam: 0.7136% posts on MathOverflow (and 0.7792% posts on Mathematics) were spam posts.
spam I see that I misunderstood the information from that post. The 0.7136% means that of all spam posts in the network, 0.7136% were posted on MO. (Not that 0.7136% of all MO posts were spam posts.)
Since some time there has been discussions about having a place for community reviews; see for example
Community Peer-Review in Mathoverflow
Such a system already working at PhysicsOverflow with considerable success.
My attempt to start something similar in MO was quickly rejected for reasons ...
Questions appropriate for a Stack Exchange-style Q&A are on topic for Mathematics SE and MathOverflow. If you would like to experiment with this type of content on MathOverflow, great; but unfortunately, we are not currently accepting proposals for new sites whose core premise is to solicit criti...