I’d say I’m making two arguments:
1) There is no distinct personal identity; rather it’s a continuum. The you today is different than the you yesterday. The you today is also different from the me today. These differences are matters of degree. I don’t think there is clearly a “subject of experience” that exists across time. There are too many cases (eg. brain injuries that change personality) that the single consciousness theory can’t account for.
2) Even if I agreed that there was a distinct difference in kind that represented a consistent person, I don’t think it’s relevant to the moral accounting of experiences. Ie. I don’t see why it matters whether experiences are “independent” or not. They’re real experiences of pain
1) I’d like to know what your definition of “subject-of-experience” is.
2) For this to be true, I believe you would need to posit something about “conscious experience” that is entirely different than everything else in the universe. If say factory A produces 15 widgets, factory B produces 20 widgets, and Factory C produces 15 widgets, I believe we’d agree that the number of widgets in A+C is greater than the number of widgets produced by B, no matter how independent the factories are. Do you disagree with this?
Similarly, I’d say if 15 neural impulses occur in brain A, 20 in brain B, and 15 in brain C, the # of neural impulses is greater than A+C than in B. Do you disagree with this?
Conscious experiences are a product of such neural chemical reactions. Do you disagree with this?
Given this, It seems odd to then postulate that even though all ingredients are the same and are additive between individuals, the conscious product is not. It seems arbitrary and unnecessary to explain anything, and there is no reason to believe it is true.