I'd suggest not so much subtle as overinterpreting. Carrow is shallow-minded and status-driven, he thinks he'll sound more deatheaterish if he puts on a particularly grim voice, and Malfoy sees right through him and tells him to stop being silly. This is simple, compatible with everything else we're told, and sufficient to explain Draco's memory described here.
I'd agree - I doubt Carrow is a Horocrux, but the repeated mentions of him might indicate that he has some further role to play, possible involving dark rituals. But the joint probability (Carrow will appear) and (his role will involve dark rituals) and (dark ritual is a Horocrux) is quite low.
Also, IIRC there are 7 Horocruxes in cannon. In HPMOR, it is hinted that we have one for each greek element (magma, ocean trench, stratosphere and buried underground) and one in space. Presumably, Harry is one and Quirrel is one. So all Horocruxes are accounted for.
New chapter, and the end is now in sight!
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 103.
There is 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.)
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: