https://twitter.com/jk_rowling/status/475975334597492736

I'm mostly numb to JKR more questionable interview / pottermore / whatever HP cannon "explanations".
And I understand that she might have done this one just to show how much attention she pays to fandom. What with tweeting answers to fans and following HP tag on Thumblr.
But this still annoyed me.
Even if you are tying to be funny and don't really like the character you've written: this still shows a incredible disdain and lack of understanding of Draco and people who like him or find him sympathetic.
no subject
Date: 2014-06-20 03:01 am (UTC)"Harry Potter and the Seven Riddles" is one that's been going around in various contexts, and might work for the Big Horcrux Reveal book.
"Harry Potter and the Unbreakable Vow" was another possibility, since we see it being made in Chapter 2 and a lot of the actual plot hinges on it. You'd probably have to add in more ominous hints over what it might be about so that Harry can worry over it; there's a bit in Snape's scene with Draco during the party, but that's about it.
It would probably work just as well to re-write the book and give it some focus so that "...the Half-Blood Prince" is actually relevant. Here's what I said back then:
"Maybe Harry could have started discovering that Snape and Lily used to be friends in this book (maybe Slughorn tells him), and then the revelation that the potions book had a Draco-eviscerating hex and Snape killing Dumbledore would feel doubly like betrayals - he wouldn't just be freaked that Snape was the one who gave Voldemort the prophecy, but that he betrayed his best friend Lily and created dangerous magic while still in school and fooled Dumbledore for years to finish the betrayal. (This would also require Harry worrying about the hexes from the book which he used and what that means about him.) He'd probably decide Snape was never a real friend, of course, being Harry. So then the Prince's tale in the next book would be not information from nowhere, but the revelation that yes, they really were friends, Snape really did want to protect Lily from the Marauders, and that he's been working essentially for Lily's memory all along. And, um, maybe playing up the Snape-as-Draco's-mentor (whom Draco is now resisting) role in all that for generational parallels and connecting subplots."