Remember what Eleizer said in the authors notes about simple vs. complex explanations? I'd default to the 'big round number' hypothesis.
I don't think that "Lucius chose the exact same number as a stab against Dumbledore" is a very complex hypothesis. We already know that he knows part of the story and can reasonably assume he knows the whole story about Aberforth. So of course if the situation already demands that he hold someone on Dumbledore's side (sort of) for ransom for some obscene amount of money, on the assumption that it won't be paid, how could he resist rubbing that bit of salt in his nemesis's wounds?
It's not part of some bigger plan. It's not some fancy maneuver. It's just an emotional attack of opportunity aimed at Dumbledore, probably just for pride's sake.
The new discussion thread (part 15) is here.
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 82. The previous thread passed 1000 comments as of the time of this writing, and so has long passed 500. Comment in the 13th thread until you read chapter 82.
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.
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: