I know there's ways to ignore people, but the fact that the person posted still shows up and they take up most of the thread and I have no idea what's going on unless I read the posts sometimes.

^that's in other people's threads. I doubt there is a way to actually block someone from replying in other people's threads, but what about your own? Is there a setting where you can say person A, B, and C are not allowed to reply to your thread?