I have never uncircled anybody (yet), but I do have a circle that's set to zero, and I've put people in it for being rude and inconsiderate, even if they have the most outstanding photos in the world. Don't care.
OTOH, most of the people I've circled are photographers, and I don't think I've circled any crappy ones because I saw them commenting on a thread. Yeah, you have a great personality, but most people found
you by your photographs in the first place.