Voldemort knows that Harry understands game theory, and has no incentive to drop his wand if he ends up dead and cannot save everyone anyway. If he orders Harry to drop his wand, Harry might refuse, and then he has to kill him before being able to extract information out of him.
There are two possible answers to this argument.
Voldemort knows Harry has knowledge he has not, but this doesn't necessarily mean Harry knows spells or has the magical power required to cast strong enough spells to harm him.
"Power he knows not" strongly implies the ability to do or achieve something, rather than abstract knowledge with no immediate applications.
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 117.
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.)