Without meaning to be fuddy-duddy about it, I'm a bit bothered by this account by a former TA. It strikes me as self-serving & unreliable, not to mention dreadfully tacky. I haven't looked at the details of the plagiarism charge, but I wouldn't hang my hat on the kind of writing a student does in a class. Maybe the class was boring? Maybe the assignments were lame? Maybe—gasp!—the TA wasn't that great . . .
You may well be right, Brendan. I certainly agree with the tacky TA comment.