One man’s modus ponens is another man’s modus tollens. I agree that the LW-style decision theory posting encourages this type of thinking, and you seem to infer that the high-quality reasoning in the decision theory posts implies that they give good intuitions about the philosophy of identity.
I draw the opposite conclusion from this: the fact that the decision theory posts seem to work on the basis of a computationalist theory of identity makes me think worse of the decision-theory posts.
Strongly seconding this.