I feel I should reiterate that I agree with you. I'm not seeing an in-universe reason for Voldemort's behavior in these two chapters either, except for maybe "He was overconfident and didn't see the need to take such excessive precautions", which isn't all that narratively satisfying, though it is somewhat realistic. (The planning fallacy is a thing, after all, and even Tom Riddle Jr. Sr. isn't immune.)
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 114, and also, as a special case due to the exceptionally close posting times, chapter 115.
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.)