The soul releasing seems easy enough to fake, as does Hermione's comment to the Patronus. Hermione being under an invisibiliy cloak near fake-Hermione would do for the Patronus taking Harry to her(though screaming mid-combat would be quite dangerous, even invisible).
The hardest part would be creating a fake Hermione sufficiently well to convince both the troll and Harry. Do we know of any magic sufficient to that task? Copying the form can be done, as was done with the Azkaban breakout, but the blood and the talking both seem outside the capabilities of that spell.
It's not obvious to me how to fake the soul releasing. It was perceived by the magic-sense, not just with the muggle senses.
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: