Warning: As per the official spoiler policy, the following discussion may contain unmarked spoilers for up to the current chapter of the Methods of Rationality. Proceed at your own risk.
Assume HPMOR was written by a super-intelligence implementing the CEV of Eliezer Yudkowsky and assorted literary critics. What would it have written differently?
... is what I want to know, but that's hard to answer. So here's an easier question:
In what ways do you think Eliezer's characterisations/world-building/plot-fu are sub-optimal? <optional> How could they be made less sub-optimal? </optional>
(My own ideas are in the comments.)
To put it another way... Assume a group of intrepid fanfic writers in the late 2020s are planning to write a reboot. What parts of Eliezer's story do you think they should tweak?
And just to make sure we're all on the same page: Eliezer isn't going to go back and change anything he's written to bring it in line with anything suggested here. This is purely an "Ah, just consider the possibilities!" thread.
... which means that we can safely suggest drastic rewrites encompassing 30 chapters or something. Or change fundamental facts about the world.
(Exercise due restraint on this one. Getting rid of the Ministry/the Noble Houses/blood purism would probably turn the story into something completely different; this isn't what we're trying to do here.)
With that, let the nit-picking begin!!
Why do wizards speak English?
Rather, why do wizards speak English that's so similar to Muggle English?
The wizard and muggle societies have been more or less isolated from each other for several centuries now (since 1692 in Rowling's canon, probably longer in Eliezer's). You'd expect a significant amount of linguistic drift to have taken place. I don't think a small trickle of Muggle-borns is enough to counter-act that.
Muggle-borns are that minority which have both parents be muggles, but there's also intermarriage between muggles and wizards/witches, so that there's a significant number of halfblood children.
And in all of UK there's only one village (Hogsmeade) that's solely composed of wizards/witches, in the rest of the country it seems that wizards/witches are surrounded by Muggle neighbours, probably with charms around them so that the Muggles don't notice anything strange, but nonetheless interacting with said Muggles...
Alternate explanation: "It's magic."