Update: Discussion has moved on to a new thread.
The hiatus is over with today's publication of chapter 73, and the previous thread is approaching 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 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. 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Eliezer Yudkowsky which is not supposed to be publicly available (which includes public statements by Eliezer that have been retracted).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.
We know that Hogwarts changes itself and has a mind of its own. We also know that Eliezer had pointed out to him in a completely distinct context that doorknobs were not invented until the second half of the 19th century. (In this thread.) In chapter 71, Eliezer explicitly mentions a door in Hogwarts having a knob. Am I overthinking or has he just given us evidence that Hogwarts is smart enough to adopt new technologies to itself?
This may not be the case since the Wizarding world does on a rare occasion adopt Muggle technology (such as the use of armor by medieval wizards). But either way it suggests that either a) wizards adopted a very late technology or b) Hogwarts has a lot of flexibility in how it behaves and can even upgrade itself. So we either have a useful sociological data point or we have a data point about what Hogwarts is capable of doing.
Hogwarts also has modern plumbing, which was presumably not put in by hand considering whoever did it would've found the chamber of secrets in that one place they put a bathroom. I think we can safely assume it will grow new features.