It's kind of an interesting thought.
I mean, we're not talking about depriving people of their fundamental liberties, here. I agree that the backbiting and Mean Girlsing that can happen in a MU* can be overblown and excessive, and the fights get nasty when the stakes are small.
But we're talking about what I do to waste my free time playing pretendyfun elfgames. If someone's made the experience actively unpleasant for me before, I'm certainly under no obligation to let bygones be bygones and walk into the same situation that turned my funtimes into a dramatic headache in the past.
And frankly... well, @Aria will tell you that I don't usually get worked up about much of anything, never mind game stuff. Anyone who does appear on what passes for my shitlist has probably pulled the "I'm doing better now" thing enough for it to go past "fool me twice, shame on me" and into "oh shut up silly woman said the reptile with a grin,/ you knew damn well I was a snake before you let me in."