i.e. it becomes clear you are using it as a sockpuppet account (some users have been caught trying to do this), outright saying you aren't black, etc.

Like if you aren't being a niche internet celebrity and aren't trying to play main character on the internet it's unlikely you'd get caught unless you were particularly stupid but that's also kinda part of the point. It's a community and people in that community know each other both online and IRL. It'd be pretty hard to be involved in the community without leaving behind an evidence trail of you blatantly lying about who you are.

Go into the subreddit "blackpeopletwitter" and just open a bunch of threads and look for someone commenting "found the white guy", or something like that.