(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Eliezer Yudkowsky which is not supposed to be publicly available (which includes public statements by Eliezer that have been retracted).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.
It's easily possible that Hermione has seen at least one picture of Sirius (she mentions him by name as the Potters' betrayer in Chapter 8), and given her memory it would be plausible for her to recognize him, even months afterward. Additionally, Sirius is one of the few people who would cause an immediate reaction of terror at first sight.
Another one might be - bear with me here - Lucius Malfoy. This idea is a little shakier, as it's less plausible that Hermione is familiar with his appearance, but the advantage is that it neatly accounts for the otherwise-strange
since Lucius seems to be convinced Harry is possessed by Voldemort. (Though it casts a certain odd light on Mr H&C's warning to Hermione about Lucius, I think it's at least possible that he could bite his tongue enough to say "though you are Muggleborn, you possess a power of wizardry greater than any pureblood" if he considered it just a flattering lie.)
The obvious antipathy toward Dumbledore and knowledge of Snape serve equally well as evidence for Lucius or somehow-evaded-going-to-Azkaban!Sirius. Interestingly, they also work for Pettigrew, who Lupin tells us "adored secrets," but who presents the issue of Hermione almost certainly not recognizing or being terrified of him.
Of course, the only reason to entertain such out-there possibilities is how weirdly clumsy and out-of-character this latest act would be for Quirrel. Mr H&C's first appearance (in Chapter 35) is really obviously Quirrel, if for no other reason than
There is that. But it's just occurred to me: if the person attacking Hermione is not Snape, then what's Snape been doing to make him late and quite exhausted in Chapter 77?