Parfit's personal identity puzzle — why it still bothers me 20 years later

Read Reasons and Persons as an undergrad and the fission thought experiment has nagged at me since. You split and both halves survive with equal claim to being "you". Parfit concludes personal identity isn't what matters — survival is. But if survival without identity is all we need, a lot of our practical commitments (punishment, promise-keeping, long-term planning) start to look differently motivated. I keep coming back to: is Parfit right, or have I just accepted the framing of the puzzle too easily? The transplant intuitions feel artificially clean.