One of the big problems with calling a canon character a Mary Sue, besides all that a_t_rain and others mentioned above, is that if you define Mary Sue as partially a self-insert, how do you know that the character is one? Unless one knows the author personally, it's a mite arrogant to say, "So-and-So is Author X's self-insert."
But why would that only apply to published authors and not fanfic?
no subject
But why would that only apply to published authors and not fanfic?