to control what posts others can see in gen pop?

If you want to ignore someone fine, that's your right, you can't see any responses they make to you, they can't BM you or communicate with you on the board. That should solve your problem, in the rare cases that this does not solve the issue get the mods involved and let them decide, or at least make them aware of it.

You are not just stopping another poster from seeing your post, you are stopping them from seeing any post that responds to you, stopping them from seeing posts from people who don't have and don't want to ignore them,

If you want to create a thread where you want to control who can respond, or even see it. Make it an FO thread.