I think I actually answered this in my last post. We agree that you would create a twin if you copied a mind of an individual. It would be completely alike at first, but ultimately they would not be the same individual/consciousness. I do not see what would be the difference if you were to destroy the original or not. Only that if you destroy the original you are left with the twin, who we agreed is not the same consciousness.
So non-destructive copy:
:
Original ---> Original ---> evolving
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Identical Twin ----> evolving
Destructive copy:
:
Original ---> Dies, goes to oblivion
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Identical Twin ---> evolving
Of course, at this point this is only my theory. It could also be as you say, even though I doubt it. Anyways, how would we ever know which one is correct?