Indeed, one of the stories at qntm features discovering something like the Fountain of Youth, and describes the organizational nightmare of letting a large enough proportion of mankind use it.
Harry Potter, however, if he makes himself immortal, will have a lot of time. Even if a lot of people die of old age or illness before he can reach them, he can still reach a lot of people given enough time. He would also need to figure out some efficient way of space travel and terraforming, otherwise he could cause overpopulation.
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 116.
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.)