Oh, I just loved this. I found this fic via Snarry Fic Find, so I already knew the twist ending. That made the doorway scene that much better. (A silver lining to a spoiled ending.
I just imagined Severus biting the inside of his cheek over having to be polite to Harry. Good job on that.
And the story progressed so well and was a joy to read. Excellent!