i think a particularly fascinating wrinkle to post amnesia doctor and civilight eterna theresa's dynamic is that for all intents and purposes, the original doctor did die.
because who else is truly left to continue the legacy of their original civilization? doctor explicitly says kal'tsit doesn't even have the full context on the creation of originum, and even if she did kal'tsit has already long chosen terra over their original civilization. pre amnesia doctor was complicit in theresas murder specifically because they were the last one left, they were burdened by the guilt of duty in ensuring that the thousands of years and billions of lives worth of effort didn't go up in smoke. And yet it did. It will.
it was theresa's revenge, after all. her little terrible trick, a final small revenge against the person who wished it didn't have to end this way. the doctor took her life, so she took theirs. 'fate' should not exist, after all. it was her fate to bear the suffering of the sarkaz, and it was the doctors fate to bear the mission of their original civilization. So, she freed them, and destroyed their fate.
Just in the same way the doctor once again freed theresa from her 'fate', able to finally pass on with the countless sarkaz before her, no longer trapped by originum. post amnesia doctor doesnt really know theresa except for the first and last conversation they had in the assimilated originum universe, but in their encounter it's incredibly clear that theresa, even though she so clearly missed them, also knows that post amnesia doctor... isnt the same person.
The original doctor already said goodbye. They faced theresa in that room where she was assassinated, filled with something far too heavy to be called guilt, and stood before her waiting to die. And even though theresa didn't physically kill them, she fractured their mind and took their memories, she took away the burden of their fate as the last survivor of their kind. She banished the evil spirit haunted by the eons of experience and sacrifice and left behind only a purified soul, nothing but a trustworthy fool who fights for the people they love.
memories can be what endures long after a person is gone, but it is the experiences themselves which shape the individual. doctor has no memories, and civilight eterna theresa only inherited all of hers. neither of them had the experiences which shaped their past selves, neither of them are really the same person as those whom everyone around them looked towards, because they can only really grow as people from there.
Their original selves died a long time ago, holding each others hands in that faraway field, and all that's left are the shadows of themselves who can grow into something new. babel's voyage had long ended, but rhodes island will continue. The Evil Spirit of Babel and The King of Sarkaz are long gone, but the Doctor and Civilight Eterna are still here.
the me who is not me and the you who is not you... it didn't work out for our original selves, but even if we are not those people, we are products of their love. it is not by 'fate' that we are here, it is love.
