In the ROTJ novelization (I believe, although this could be from somewhere else), Yoda is the one that makes it possible for Anakin to become a ghost at the end and see his son. I don't believe this was done due to Anakin being redeemed, but was done for Luke. Luke deserved to see his father as a Jedi. And then Anakin can drift back into the madenning abyss that all Sith are destined for. I dont think retaining your identity can be classified as a redemption from hell. The only real purpose to retaining your identity after death is to help the living.