(The HPMOR discussion thread after this one is here.)
The previous thread is over the 500-comment threshold, so let's start a new Harry Potter and the Methods of Rationality discussion thread. This is the place to discuss Eliezer Yudkowsky's Harry Potter fanfic and anything related to it. The latest chapter as of 09/09/2011 is Ch. 77.
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: one, two, three, four, five, six, seven, eight. The fanfiction.net author page is the central location for information about updates and links to HPMOR-related goodies, and AdeleneDawner has kept an archive of Author's Notes.
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:
You do not need to rot13 anything about HP:MoR or the original Harry Potter series unless you are posting insider information from Eliezer Yudkowsky which is not supposed to be publicly available (which includes public statements by Eliezer that have been retracted).
If there is evidence for X in MOR and/or canon then it's fine to post about X without rot13, even if you also have heard privately from Eliezer that X is true. But you should not post that "Eliezer said X is true" unless you use rot13.
Has it occurred to anyone else how good magic would be for psychological experimentation?
To start with, imagine you get the consent of your subjects to be Obliviated. Then, you can try exposing the subjects to differing stimuli while they're in exactly the same starting state, and you can precisely and easily measure the effect of whatever change you've made.
Even better, imagine the marketing opportunities. Think of Mr Hat and Cloak's dictionary attack, but with a focus group, and different advertisements for your new product. Show them the ad, then ask them how much they liked it, then Obliviate them again.
Also, you could try to remove the effect of priming on yourself with self-targeted obliviation.
And you could go on 4chan, knowing that what has been seen actually can be unseen, leaving you with only a note saying "Don't look at SqueeHorse" or something.
I really want magic.
Somewhere on LW, I think, someone suggested that 'discovering perfect psychological manipulation' was a problem akin to NP - hard to find, easy to check. So give rationalist!Voldemort a time-turner, a servant, and a a dungeon...