Even further proof that Harry's goodness is nothing to do with his actions - or indeed even his personality - but is instead some kind of elemental property comes from this rather interesting quote, regarding the fact that Voldemort had hope of salvation:
"Because he had taken into his body this-- this drop of hope or love (Harry's blood). So that meant that if he could have mustered the courage to repent, he would have been okay. But, of course, he wouldn't. And that's his choice."
Now there's two interesting things here. The first is that Voldemort's hope came literally from Harry's blood. Voldemort is not a person, Harry is not a person. Harry is a vessel full of Hope and Love in distilled form. No matter how many people he tortures or brutalises, he will always have Hope and Love in his very blood. It is physical contact with Harry's blood that gave Voldemort his one chance of redemption.
The second, subtler point is this one:
"But, of course, he wouldn't. And that's his choice."
Notice that she uses the words "of course" and "his choice" in the same sentence. And this is the point I find most interesting.
If you ever try to argue that JK Rowling is a slavering determinist, people always pull out two facts. Firstly, there's the fact that Harry "chose" not to be placed in Slytherin. Secondly, there's this extremely interesting line by Dumbledore.
"It is our choices Harry, that show what we truly are, far more than our abilities."
Now I hope it doesn't look like I'm being obsessive here, but I think it's extremely telling that Dumbledore uses the phrase "show what we truly are" and not " say "decide what we become." Dumbledore is telling us, quite clearly, that who we are never changes, that the decisions we make in our lives serve only to illuminate our natures, which are otherwise immutable.
So Voldemort could never have been redeemed. He was given the chance to "try for some remorse" but there was never any realistic expectation that he would be able to. Indeed we are told repeatedly throughout the series that Voldemort is not capable of love. Not that he hasn't known love, that he has never experienced love, that he is literally
incapable of it.