I agree that this task is far "easier task than a standard AI box experiment". I attacked it from a different angle though (HarryPrime can easily and honestly convince Voldemort he is doomed unless HarryPrime helps him).:
http://lesswrong.com/r/discussion/lw/lsp/harry_potter_and_the_methods_of_rationality/c206
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: