You join a party that is in pf, someone on your blist is there, you leave. It's that simple, if you feel bad because you took the last spot send the leader a tell. However The whole pint of blist someone is so that you don't have to hear from them so even if they are in the same party as you i if it isn't the leader, how much does it matter? 0%-10%(if they are friends with the leader). I have no issues running things with people I have blisted as long as they aren't in a leadership position. There are people whom name I memorized and will not run stuff with because they are awful and refuse to accept their faults. I'll join, leave and send the leader a tell if I took the last spot apologizing and it also reminds them to put df back up. if you get them in a dungeon for DF and they harass you or troll your party then guess what SE has a system for that, in which your offender will get temporally banned if he is in fact an offender.