I think the simpler "conscious Horcrux inside Harry" theories are ruled out by the sorting hat: "I can tell you that there is definitely nothing like a ghost - mind, intelligence, memory, personality, or feelings - in your scar. Otherwise it would be participating in this conversation, being under my brim."
It is possible that the original, canon Harry has been completely replaced by Voldemort, or that the Horcrux has merged with Harry to form a new single personality. The sorting hat is also explicit that it does not remember previous students such as Tom Riddle as individuals. Therefore it would not notice if HJPEV were in fact Tom Riddle redux. However there's just one person in Harry, not two.
The hat talked specifically about objects under its brim. Maybe the horcrux is in some other part of Harry?
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 88-89. 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, 18.
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: