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...
If every action taken against an account by automation is appealed, then the automation becomes worthless.
In gaming forums that are run by the developer, such as the World of Warcraft or League of Legends forums, I have very frequently seen people whining and complaining that their accounts were banned for no reason until a GM or moderator finally pipes in and posts chat logs of the user spamming racial slurs or some other blatant violation of ToS.