Last time I did this, it was to argue that Remus was evil, and that was Moony’s fault as well.
The following contains references to all five books, and under the cut is an extract from JKR’s website and an analysis of the American cover of HBP that may be construed, for the very paranoid, as spoilers. You have been warned.This sacrifice turned out to be vitally important, for it was the ancient magic of this act that protected the child. When Voldemort's Avada Kedavra curse hit Harry, the protection of Lily's sacrifice made the curse rebound onto Voldemort, who was all but killed. The curse left a curse scar in the shape of a lightning bolt on Harry's forehead.
- from the Harry Potter Lexicon.
Recently, I asked my friends list why they thought Voldemort was "killed" that night in Godric's Hollow
. (Or at least, injured enough to need to possess animals and disappear for about ten years.) The answer was basically the same as what the Lexicon has to say. However I believe that this is another example of fanon, fandom and the movies digging into the perception of canon.
Dumbledore says: “Your mother died to save you. If there is one thing Voldemort cannot understand, it is love. He didn’t realise that a love so powerful as your mother’s for you leaves its own mark. Not a scar, not a visible sign… to have been loved so deeply, even though the person who loved us is gone, will give us some protection forever. It is in your very skin. Quirrell, full of hatred, greed and ambition could not touch you for this reason. It was agony to touch a person marked by something so good.” [PS/SS.]
However I do not believe that this “marking” is why the curse injured Voldemort – nor indeed that is the true reason the curse rebounded and set the prophecy in motion in the first place.
So what was the real reason? Dumbledore says “We can only guess… we may never know.” [PS/SS.] JKR says “for some mysterious reason, the curse didn't work on Harry.” Dumbledore is unsure about it for so long in the books – surely the solution of Lily dying for Harry would have been obvious from the very first? Voldemort, too, is confused as to why the curse rebounded and killed him.
It is Harry who makes the assumption that fandom believes as fact. “No-one knows why you lost your powers when you attacked me,” said Harry abruptly. “I don’t know myself. But I know why you couldn’t kill
me. Because my mother died to save me.” [CoS.]
Riddle muses on this, believing that it was just pure luck. However numerous interviews from JKR state that this is not the case at all; that Harry is an exceptionally powerful wizard who is growing into his powers, and that Voldemort's non-death is important to the future plot.( a short theory for the contents of HBP )