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...
From the user's perspective, it's still a pretty good deal. There's a 99.999% chance that you get to use gmail/youtube/etc for free. And a 0.001% chance that you'll end up a statistic, and need to pay a nominal fee for an appeal.
Unfortunately, I don't think the above will ever happen, because it would be a PR nightmare. "Google wants to charge you money, just to appeal a ban!" It's still better than the status quo, where people have almost no recourse when they are banned. But it still sounds way better in the media, if you just pretend as though these things never happen. Hence the status quo - use automated systems to cheaply get to a 99.999% success rate, and spend as little money as possible on the remaining 0.001%