“We scatter parts of our soul when we sin, and if we don’t stop, soon we will find our souls empty.” —author Angela Hunt

JKR: One of the things on there was- it’s about the end, and how Harry survived right at the end, when he doesn’t fight, and Voldemort uses the Killing Curse on him. Well, it was important for me to say on the website, I never saw this- as in the finale, the denouement, the moment when Harry faces Voldemort, is prepared to die, and yet doesn’t die- that isn’t like a scientific equation. Harry- it’s not guaranteed. There has to be space, to make Harry truly heroic, for free will. It has to be his choice. The whole thing’s his choice. He chooses to sacrifice himself, just as Lily chose to sacrifice herself. He chooses to pull himself back to life. And that’s his own will and courage. So ultimately, those things, all of them were more important than the magic.

There is another inconsistency concerning horcruxes, I think.

After his death, Dumbledore tells Harry: ‘You were the seventh Horcrux, Harry, the Horcrux he never meant to make. He had rendered his soul so unstable that it broke apart when he committed those acts of unspeakable evil, the murder of your parents, the attempted killing of a child. But what escaped from that room was even less than he knew. He left more than his body behind. He left part of himself latched to you, the would-be victim who had survived.’
In the Bloomsbury Live Chat JKR also calls Harry ‘the last and unintended Horcrux’.

But Harry wasn’t the last Horcrux, Nagini was. Whether Voldemort made it by killing Frank Bryce (as Dumbledore suggests) or Bertha Jorkins (as Rowling says) – it was about 13 years later and Voldemort was not in a healthy condition. But this time his evil deed did not weaken him at all, it seems.

Arabella and Revgeorge, you are probably right in that we should not try to nail the author down to every detail she wrote or said. It’s not all important to the story. It just seems to be to those who read the books dozens of times and think there must be a meaning that can be decoded in every single bit. And we all tend to be like that to some degree or another

Arabella Figg, I wondered the same thing about time elapsing between murder and Horcrux making. I also think you’re right about some plot points being done for convenience. Creating a story and preserving the inner logic is hard work, after all.

Lily Luna, I can’t think of a time in PS where we learn that Lily and James had any contact with Voldemort whatsoever before he killed them. As a matter of fact, it seems to me that the first time I heard anything about their having “thrice defied him” was in OotP when Dumbledore tells Harry of Trelawney’s prophecy. I might just be missing it.

Not that she needs a defense, but just because the thought came to mind: As far as clear recollection of the story’s details and logic goes, Rowling is at a disadvantage against those of us who read and re-read the books. As I know from dabbling in fiction myself, a writer’s mind is a mess of nebulous backstory and potential plot lines and directions that happened in chapter 25 that meant going back and changing details in chapter 2. The best mind-maps in the world aren’t insurance enough against confusion.