EDIT: New discussion thread here.
This is a new thread to discuss Eliezer Yudkowsky's Harry Potter and the Methods of Rationality and anything related to it. With two chapters recently the previous thread has very quickly reached 500 comments. The latest chapter as of 17th March 2012 is Ch. 79.
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.
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:
You do not need to rot13 anything about HP:MoR or the original Harry Potter series unless you are posting insider information from Eliezer Yudkowsky which is not supposed to be publicly available (which includes public statements by Eliezer that have been retracted).
If there is evidence for X in MOR and/or canon then it's fine to post about X without rot13, even if you also have heard privately from Eliezer that X is true. But you should not post that "Eliezer said X is true" unless you use rot13.
First of all: Dumbledore has visibly just traded Hermione for his own position (so that's one trade-off).
But besides that I find one hypothesis that answer your questions within the given parameters (more might dot my mind later, hence I'll number it from the get go):
The dark part: betraying a promise.
Now the social part: Now he has let everyone in the Wizengamot see that Draco is willing to torture another kid until this kid dies/goes crazy. And this is not ANY other kid; it is The-Boy-Who-Lived.
Next Harry could ask them if they then thought it beyond Draco to have Hermione and himself false-memory charmed/obliviated so as to both get revenge over Hermione who publicly humiliated him (which Harry hadn't) AND regain his lost honour by appearing victorious in the false memory.
For kicks he could throw in the mudblood/true born-equality discovery (and that would also qualify for the taboo-part).
... Lucius would severely regret having earned that enmity. Dark side should like this.
Oh, and about the laws: this should have Draco, and thereby the House of Malfoy, owe a blood debt. This blood debt could be used to either: a. let Draco suffer the same punishment as Hermione (a good way to make sure none of them get hurt too badly) b. let him take her place (a way darker way of dealing with Lucius) (unlikely due to the sheer amount of harm done; too dark) c. have Lucius revoke his vote (uncertain about the legality)
Another option when it comes to Magical Britain's laws might be invoking some duel right. I do not know if this is possible, but it would be in line with the medieval feel of Magical Britain.
We would object that laws cannot be changed retroactively. Magical Britain doesn't follow a constitution so I cannot see why not.
Besides that I suppose a duel might actually invoked to defend Hermione's honour. I'm really uncertain about that though.
Draco isn't even present. His earlier testimony under Veritaserum was simply read aloud.
And also the possibility of utilizing Draco's use of torture was mentioned and rejected in the previous chapter, as Lucius Malfoy may well have obliviated anything incriminating he found in Draco's mind under his own Veritaserum interrogation of his son.