As Quirrel said in his very first class
If, for any reason, you find yourself incapable of casting the Killing Curse
So it's surely not unheard of.
Canonically, I think it also took substantial magical power to be able to cast it, so I suspect that the average adult witch or wizard wouldn't be able to use it (most ordinary adults were made out to be fairly incompetent at the magical skills they didn't use regularly,) but Quirrel seems to be imposing rather higher standards on his students.
I wouldn't be surprised if Quirrel could recall emotions - I was only defying the claim that "any one of us" could do so without much trouble and am using the counter example of me.
The new discussion thread (part 15) is here.
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 82. The previous thread passed 1000 comments as of the time of this writing, and so has long passed 500. Comment in the 13th thread until you read chapter 82.
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.
As a reminder, it’s often useful to start your comment by indicating which chapter you are commenting on.
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: