[quote=Tydosius]
I'd say that the definition of a Mary Sue is a character who never experiences internal struggle in the events of the narrative or can never experience internal struggle in the events of any narrative. Would you agree? Or would you say this is derailing a perfectly sufficient thread?
[/quote]

I would generally say that a Mary Sue is one with no flaws as they are intended to be perceived, but I would definitely say that's an argument for another thread.