I interpreted it as Harry being jolted out of his all-consuming inner monologue by Dumbledore suddenly touching his shoulder while he wasn't paying attention to Dumbledore at all.
But Harry didn't see anything helpful he could do using spells in his lexicon, Dumbledore wasn't being very cooperative, and in any case this was several minutes after the critical location within Time
"Harry," the Headmaster whispered, laying his hand on Harry's shoulder. He had vanished from where he was standing over the Weasley twins and come into existence beside Harry; George Weasley had discontinously teleported from where he was sitting to be kneeling next to his brother's side, and Fred was now lying straight with his eyes open and wincing as he breathed. "Harry, you must go from this place."
He wasn't paying attention at all to Dumbledore, Fred, or George, and he's startled by their sudden agency. To me it seems more likely that leaving off in the middle of a sentence as he's startled is a stylistic choice, rather than a particularly meaningful missing period.
This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapter 90. The previous thread has passed 750 comments.
There is now a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author’s Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)
The first 5 discussion threads are on the main page under the harry_potter tag. Threads 6 and on (including this one) are in the discussion section using its separate tag system. Also: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,18,19.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: