It's interesting that in Ch 81 Lucius (acted like he) didn't know that Harry can cast a Patronus.
In Ch 79, Dumbledore suggested:
Harry... whatever you have done with Draco, you must assume that Lucius Malfoy will soon know of it."
Harry's head sank into his hands. "He'll give Draco Veritaserum."
But apparently Lucius decided to let Draco keep some privacy.
Or he just hasn't gotten around to fully questioning him under veritaserum yet.
Or he's pretending that he doesn't know that Harry has a Patronus.
Or someone obliviated Draco of this information before Draco was returned to his father.
Or Draco is secretly an occlumens and he just pretended to let the veritaserum work on him.
EDIT: Never mind, there's a comment in the new thread about it.
The new thread, discussion 13, is here.
This is a new thread to discuss Eliezer Yudkowsky's Harry Potter and the Methods of Rationality and anything related to it. With three chapters recently the previous thread has very quickly reached 1000 comments. The latest chapter as of 25th March 2012 is Ch 80.
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: one, two, three, four, five, six, seven, eight, nine, ten, eleven.
As a reminder, it's often useful to start your comment by indicating which chapter you are commenting on.
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: