Because the same tactic wouldn't work again. And this time, he has Lucius Malfoy to pin it on.
Waitaminute...how exactly have we gotten this far without considering the possibility that Lucius did this? It seems tailored to the protections on Hermione more closely than he would usually be able to manage, but he'd know the Hogwarts wards as well as anyone who wasn't Headmaster, and the "eating the feet first" bit could be coincidence. And plausible deniability plus brute force seems exactly like Lucius' style.
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 88-89. The previous thread has passed 500 comments.
There is now 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.)
The first 5 discussion threads are on the main page under the harry_potter tag. Threads 6 and on (including this one) are in the discussion section using its separate tag system. Also: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: