He's also a Horcrux in canon; the murder that created him was the murder of Harry's parents, which still happened.
It wasn't the murder of Harry's parents, it was
when Lily cast her own life between them as a shield, the Killing Curse rebounded upon Lord Voldemort, and a fragment of Voldemort’s soul was blasted apart from the whole, and latched itself onto the only living soul left in that collapsed building.
(Deathly Hallows, Ch 33)
The Killing-Curse-reflecting Love Shield doesn't exist in HPMoR, so if Harry is a Horcrux it's not because things happened the same as in canon.
Sirius somehow got everybody to convict and incarcerate Pettigrew in his place (Imperius + repeated doses of Polyjuice?).
He wasn't even convicted, just tossed straight into Azkaban. And another piece of evidence is the Quibbler article claiming Pettigrew and Sirius are the same person.
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 87. The previous thread has passed 500 comments.
There is now 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.)
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: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17.
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: