I actually enjoy the negative list I am growing with this approach.
My alts have been removed from groups at dungeon entrance without any feedback and I saw the group resurface in LFG = I don't want to play with such people, so I blacklist them for myself.
My alts have been declined from content they are very comfortable facerolling (if you based your decision on actually checking their gear, which shows where I got it from - which dungeons and how high the key was) and the group is still in LFG for long periods = I don't want to play with such people, so I blacklist them for myself.
You see - there are so many players out there, I don't mind blacklisting even hundreds of those I don't want to spend time with. I treat a "silent removal" or "decline from faceroll content while waiting for someone with over-the-top something instead" as signs of a mind-set I am not keen on sharing. Just another information about a player (the party-leader in this example) I can act upon and improve my gaming-time quality in the future.
I apprieciate all the great people I met in pugs and we added each-other in btag, on the other hand! They are great and I love finding such gems in the pug-hell