Aww. The scene with Harry's marking was born very early on in the story notes as soon as the concept of red right hand formed in our minds. The tone of that scene: the motivation, the tentativeness, the significance of Harry asking to be marked remained pretty much the same till the end. I just hope we were able to convey most of it to the readers. I think I was so attracted to the idea of red right hand because it resonated in my mind with all the classic snarry plots: the stigma of teacher/student, death eater/hero relationship and the world that is so quick to condemn them for it - only here there's absolutely no way to hide the stain of association as there's no way to hide a red handprint. Either way, Harry handles it with all the heroic, rebellious subtlety that can be expected of him. :)