Is she particularly powerful, though? She's extraordinarily talented, very knowledgeable for her age, and has more raw power than anyone in her year including Draco; but Rita is more experienced, and most importantly older - it has been repeatedly pointed out that HP lacks the raw power for something-or-other, and the twins are far stronger than he despite not being particularly talented. It seems that Rita should have an edge in the "raw power" department, and I'd expect this effect to key off raw power.
Note that it's also sufficient to assume that Quirrel and/or Mary's room can suppress this effect.
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 94. The previous thread has passed 200 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, 19, 20, 21, 22.
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: