Personally, I don't think that the "scar" thing really helps anything. I think she was just trying to destract from everything else.

What I meant with the memory thing, was that Harry stabbed the diary with the tooth, which was the memory, so that memory no longer exists, right? If he HAD come back to life, I think that there would be some sort of spell to combine the people, or Voldemort would've gotten info from him, and then put him as an undercover person or something.

Okay, I think that since there is no way for Harry and Voldemort to live together, something has to die. As we know, Harry survived the curse, so maybe Voldemort could do the opposite - die under protection. As we can tell, anything is possible.

Also, maybe it's that they both have to die in order for others to live.