McGonagall's wording ("trapped outside Time") suggested to me that she knows at least the basics of where Dumbledore went.
She's just repeating what Harry said in Chapter 116:
"Dumbledore's gone!" cried Harry Potter. "The Headmaster is gone, Professor McGonagall! The Dark Lord trapped him, he reversed some kind of trap the Headmaster planned and Dumbledore was caught outside Time, he's gone!"
I can't imagine she'd just accept that without asking for some kind of clarification, or putting the pieces together herself -- I get the impression that the presence and general properties of the Mirror were common knowledge among faculty (what with everyone in Gryffindor having run the dungeon), though the details of Dumbledore's plan couldn't have been.
But fair enough, I'd forgotten that bit.
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 118.
Plans for next chapter release:
There is 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.)