At that level, "percentage" is an insufficient measure. You want "permillionage", or maybe more colloquially "DPM" for "Defects Per Million" or even "DPB".
You'll still get false positives though, so you provide an appeal process. But what's to prevent the bad actors from abusing the appeal process while leaving your more clueless legitimate users lost in the dust?
(As the joke goes: "There is considerable overlap between the intelligence of the smartest bears and the dumbest tourists" [1])
Can you build any vetting process, and associated appeal process, that successfully keeps all the bad actors out, and doesn't exclude your good users? What about those on the edge? Or those that switch? Or those who are busy, or wary?
There's a lot of money riding on that.
[1] https://www.schneier.com/blog/archives/2006/08/security_is_a...