The ignore list only hides the specific content of a post by that person--you still see that that person posted, you just don't see the post text itself. It's the same thing with a thread. If the person on your ignore list is the OP of a thread, then the OP doesn't show up for you. If someone else quotes his or her post, then you will see it. (I think...I put one person on ignore briefly many years ago and I don't think that I have that capability now, so I'm going from memory.)
I'm not sure what the intent is here. Do you want that person to disappear comletely for you on BARF? We don't have that ability. Depending on what you want to do, we might be able to guide you to take actions that will help.