Your points are good, and I understand what you are saying, and that probably is enough reason to accept why Lucius is not imperioing people in the story, without positing that you cannot bind an Unbreakable Vow while under an Imperius.
However, with that said, I don't think you understand just how powerful the Unbreakable Vow is. There is a reason why EY nefed it so much in HPMOR, and if you can simply get around that with a simple Imperius curse... Maybe in this alternate world the Imperius curse would still be illegal, but I doubt it. Because the people who use the Imperius curse have the full power of the Unbreakable Vow at their backs, and they would quickly have the laws changed to their whims.
("But how is the Unbreakable Vow that powerful?" some may ask. Well, it is a complete and utter solution to any game theoretic problem, at all. For example in the one-shot prisoner's dilemma, the Nash equilibrium is Defect-Defect. But if you use the Unbreakable Vow, you can get both sides to Cooperate. (And both sides will agree to the Unbreakable Vow because Cooperate-Cooperate gives them a better result than Defect-Defect.) And so much of your normal human interaction is that kind of game, which is trivially solvable if you have such a powerful commitment mechanism.)
A (non-nerfed) Unbreakable Vow is even more powerful than that. A person under an Unbreakable Vow is an AGI programmed in human wetware by a human using nothing more precise than ordinary words. Leaving aside FOOMs based on hardware speed and recursive self-improvement, the entire content of the sequences about AGIs and Friendliness applies.
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 87. 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.
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: