Trolls do grow up, as previously notied.
Point of pedantry, but we don't actually know that. It is possible that they spawn into existence full-grown as part of some magical process (fission, perhaps), or that their regenerative powers don't activate until they've grown to adult size. For the latter, it's not like they don't have enough other natural defenses to protect them until they reach adulthood.
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 113.
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.)
IMPORTANT -- From the end of chapter 113: