Falling profiles on scale might be hard, but so is verifying wherever they are real. If you have only even 20 commenters replying to one of your comments, then you're gonna spend the rest of the hour digging through them to figure out which are bots and which aren't.

The comment history is not visible on every relevant platform, and there are good reasons for people to disable it where possible. Furthermore, many people keep their profiles minimal out of principle. Hard to distinguish those from bots.