... prevent claimed users (which/who are in fact bots)...
In the above sentence, what's the most appropriate choice to refer to the users that are in fact bots? I think, which is correct one, however I'm afraid of grammatical mismatch. Of course, using that can solve the problem, by the way.
I think you can use either and it would be acceptable. However, you already anthropomorphized them by using the verb claim, so it would be consistent to use who to refer to them. If you changed that phrase to something less active, such seemingly human users, it would then be more appropriate to use which.
This is very interesting. I am not 100% sure of my answer but just throwing it out here.
It depends what the noun of the sentence is or more specifically what they first of are.
Are they before anything Users or Bots?
In my opinion, bots are users too and users are people so by extension; bots are people too and for people the correct pronoun would be "Who".
So personally, I would use who. But with that said, which can work as well if you analyse it differently.
