There's usually telltale signs if a user was misquoting (the odd [/quote] tag, context within the post, strange formatting) rather than plagiarizing. I mean adding "" isn't that difficult, even when typing on a phone. theymos even recently unbanned a user that he deemed to have only misquoted content rather than plagiarizing it:
OK, he's unbanned. He did post quotes without attribution, but I'm convinced that he wasn't doing this to pad his post count or anything like that, and he just failed to quote & attribute in the proper manner.
So if you make mistakes but your intentions weren't to profit off of other people's hard work, the possibility of getting your account unbanned isn't completely out of the question.