Did you not read that section at all? If you lose all knowledge of powerful spellcasting, a) you lose your ability to continue to be immortal after this iteration, b) you lose your ability to defend yourself against enemies who haven't lost their ability to cast interdicted spells. The second one is really important when the process for immortality is one that inherently makes a lot of enemies! He specifically mentioned that dark wizards that tried use that technique to come back were easily defeated afterward.
Could that explain why Hat&Cloak seems to be a clever manipulator who works in utmost secrecy? (They really are weak, and survive only by hiding in the shadows.) We never see them indicated as using anything more complex than an Obliviate or disguise spell, AFAIK, which any reasonably competent adult wizard would be able to pull off.
New chapter!
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 102.
There is 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.)
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: