The silver outline blasted back into the world, and said in the strange outside version of Harry's own voice, "Hermione Granger says," the blazing figure's voice became higher-pitched, "AHHHHHHHHH!"

Do Hermoine's parents even have the right to withdraw her? Harry's parents apparently do not have such a right:

Muggles had around the same legal standing as children or kittens: they were cute, so if you tortured them in public you could get arrested, but they weren’t people. Some reluctant provision had been made for recognizing the parents of Muggleborns as human in a limited sense, but Harry’s adoptive parents did not fall into that legal category (Chapter 26).

We know that LL loves his mother, but does she love her son? Does she love anyone but Voldemort?

Saved by the Wayback Machine. Thanks. I should have checked the talk page.

WPDR Harry could at least drink HPJEV under the table.

This is the quote I had in mind, from Chapter 23 of HBP:

‘He [Voldemort] seems to have reserved the process of making Horcruxes for particularly significant deaths. You would certainly have been that. He believed that in killing you, he was destroying the danger the prophecy had outlined. He believed he was making himself invincible. I am sure that he was intending to make his final Horcrux with your death.

‘As we know, he failed. After an interval of some years, however, he used Nagini to kill an old Muggle man, and it might then have occurred to him to turn her into his last Horcrux.

If Dumbledore is right, then Bertha Jorkins could not have been murdered to make that Horcrux, because she was already dead. Is there an interview where Rowling says otherwise? I don't see anything on the wiki page (a citation, or other reference) that backs up their claim.

I thought that the Nagini horcrux was made via the killing of Frank Bryce. Don't have the book with me to check, though.

Right here.

I'm assuming the 'past-Quirrell' that Quirrell tells Hermoine about in Chapter 84 is the 'young man' that Amelia Bones believes is now Quirrell. (Is this reasonable?)

If that's the case, then one way of understanding the situation is this: Riddle assumed two personas---Voldemort and Light Riddle---in order to experiment with different ways of acquiring power. He found that the Voldemort-path was much more preferable on account of the loyalty he could obtain via the Dark Mark. The Dark Mark was so effective that the loyalty he earned as Light Riddle seemed negligible by comparison; thus he complains that he got no help from his 'allies'.

So Riddle retired his Light persona by faking his own death and continued only as Voldemort. Now that he sees Harry as a potential puppet, he wants to ensure that he/Harry have loyalty comparable to that secured with a Dark Mark. He therefore calls for a 'Light Mark' in his speech before Christmas.

EDIT: Of course 'Light Riddle' (if he existed) and Voldemort would have looked different; Minerva remembers Voldemort as snake-like. If the above is right, then Voldemort's disfiguration would have to be a disguise rather than real damage from Dark Rituals.

It can't be blocked by raw magic (Protego and similar) but what prevents Actio, Wingdarium Leviosa or Free Transfiguration to be used to create a physical barrier to block the spell?

Nothing. Indeed, Dumbledore blocks the killing curse in canon (Order of the Phoenix) by animating a statue to jump in front of it.

So if AK is in any way unblockable, it is unblockable only by magical means.