As I mentioned a few times, HPMoR time turners violate general relativity, as they result in objects appearing and disappearing without any energy being extracted from or dissipated into the environment. E.g. before the loop: 1 Harry, during the loop: 2 Harries, after the loop: 1 Harry.
Yes, but you could very well think about something equivalent to the time-turner that exchange matter between the past and the present, instead of just sending matter to the past, in a way that keeps energy conservation. It would be harder to use practically,but wouldn't change anything to "energy conservation" vs "determinism" issues.
This is a thread where people can ask questions that they would ordinarily feel embarrassed for not knowing the answer to. The previous thread is at close to 500 comments.