Although Elizier has dealt with personal identity questions (in terms of ruling out the body theory), he has not actually, as far as I know, "solved" the problem of Personal Identity as it is understood in philosophy. Nor, as far as I know, has any thinker (Robin Hanson, Yvain, etc) broadly in the same school of thought.
Why do I think it worth solving? One- Lesswrong has a tradition of trying to solve all of philosophy through thinking better than philosophers do. Even when I don't agree with it, the result is often enlightening. Two- What counts as 'same person' could easily have significant implications for large numbers of ethical dilemnas, and thus for Lesswrongian ethics.
Three- most importantly of all, the correct theory has practical implications for cryonics. I don't know enough to assert any theory as actually true, but if, say, Identity as Continuity of Form rather than of Matter were the true theory it would mean that preserving only the mental data would not be enough. What kind of preservation is necessary also varies somewhat- the difference in requirement based on a Continuity of Consciousness v.s a Continuity of Psyche theory, for example should be obvious.
I'm curious what people here think. What is the correct answer? No-self theory? Psyche theory? Derek Parfit's theory in some manner? Or if there is a correct way to dissolve the question, what is that correct way?
That's not my argument - rather, I simply point out the highly limited usefulness of dividing the space of concerns into "altruistic" versus "self-interested" categories. These are not two different kinds of concerns (at least to a clear-headed reductionist), they are just two different locations, or directions of concern. Without locating the concern in a history and causal trajectory, and just looking at the felt quality of concern, it's not possible to categorize it as "self" or "other".
You said earlier:
That alleged contrast is what I find wanting.
I don't have any objection to taking a 4D view of objects, including people. Whatever works for the task at hand. I also don't reject the concept of personal identity; I just put it in its place.
A lot of what is valuable in life requires a long time-horizon of highly integrated memory, intention, and action. Normally (but not by any necessity) those long spans of highly coherent activity occur within a single person. There is more to life than moment-to-moment well-being. So I would agree that your first scenario is better - in almost all cases.