I don't think "It was not a vow he could break even by sacrificing his life in the process" means what I think you may think it does.
(I think it means something like "Harry can't, and won't, say 'Oh, screw it, I'll destroy the world' at the price of dying. He simply, will not make any choice that in his judgement risks destroying the world". Note that this leaves entirely open the question of whether anything could release him from this constraint. Of course the word "Unbreakable" in the name is something of a giveaway; but I am not aware of anything in either canon or HPMOR that rules out the possibility that such a vow is somehow tied to the vower's brain, or ceases to exist on their death for some other reason.)
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 113.
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.)
IMPORTANT -- From the end of chapter 113: