which has some as-of-yet unspecified implication for the merit of his position

See Furcas's comment.

that allows him to see his life as no different from any others and yet still act in preference to himself

I never said it was no different. Elsewhere in the thread, I had argued that selfishness is entirely compatible with biting the third bullet. Egan's Law.

And it was obvious what distinction he was making by using the words "very roughly the same reason" instead of "exactly the same reason".

I disagree; if it had been obvious, I wouldn't have had to point it out explicitly. Maybe the cognitive history would help? I had originally typed "the same reason," but added "very roughly" before posting because I anticipated your objection. I think the original was slightly funnier, but I thought it was worth trading off a little of the humor value in exchange for making the statement more defensible when taken literally.

I'm sorry, but that's just not "how it works". [...] your full explanation [looks] blatantly ad hoc.

I'm curious. If what actually happened looks ad hoc to you, what's your alternative theory? If you don't trust what I say about what I was thinking, then what do you believe instead? You seem to think I've committed some error other than writing two admittedly somewhat opaque comments, but I'm not sure what it's supposed to be.