(A) If there's a possibility that what Miles Teg thinks of as his one and only lifetime is actually his second (or third or more) lifetime?
(B) If we rewound the universe to a billion years ago, and let it develop from there according to its quantum probabilities, and did this over and over, what fraction of these universes would contain Miles Teg?
I think (A) is physically impossible, given the actual biology and physics of human minds and bodies. But I won't argue for that or even try to explain why.
I think (B) is a very interesting question, and what's interesting about it is that it's ill-posed. It's like asking, "What is the maximum number and lengths of hairs on your head that you can have and still qualify as bald?" It's not just that we'll never KNOW the answer. The question doesn't HAVE an answer. "Baldness" is inherently a vague concept. And so is "Miles Teg". In an alternate history, someone genetically just like our Miles Teg is born a year earlier - or a decade - or a century - and has different experiences and takes on a different personality as a result. Same person? There is no right answer. Again, it's not just that we don't KNOW the right answer: we can specify details of the alternate history until we're blue in the face, and it makes no difference. The question is not factual, it's pragmatic - it's about how we want to use the words "Miles Teg", or more generally, "same person".
That doesn't mean that anything goes. We can't say that in an alternate history, a fire hydrant would be Miles Teg. But we do have a wide latitude of reasonable options to choose from. Just as we can draw the cutoff line for "bald" at any of a variety of reasonable points, we can require various amounts of psychological and/or physical commonality before calling these hypothetical people "Miles Teg".
Now apply these points to the case of making two copies of a person. Say I'm strapped unconscious to a table, and a "copy machine" records my exact brain and body states down to the last neurotransmitter. Unfortunately, it has to pick apart my brain and body to get access to this information, leaving a pile of scraps on the floor. But not to worry! The machine makes TWO faithful, exact copies based on the information, using fresh proteins, fats, calcium, etc., mixed with equal portions of recycled scraps. When the machine finishes, the doctors write "A" in magic marker on one guy and "B" on the other guy. They wake up.
The question y'all have been asking is, which is the real Ayatollah So? A? B? Neither? Both?
Well, I would discourage a too-hasty assumption that the question has an answer. But - and this is the really really important point - if it does have an answer, it
might still be the wrong question.
Here are some more useful questions: how should Ayatollah So on the day before the operation regard guys A and B? How should his friends and loved ones react? These questions, I think, DO have definite answers. And the answer to all of them is "Both", i.e., both A and B are rightful claimants to the legacy of Ayatollah So.