I’m hesitant to get into a terminology argument when we’re in substantive agreement. Nonetheless, I personally find your rhetorical approach here a little confusing. (Perhaps I am alone in that.)
Yes, it’s annoying when people use the word ‘fruit’ to refer to both apples and oranges, and as a result confuse themselves into trying to derive propositions about oranges from the properties of apples. But I’d suggest that it’s not the most useful response to this problem to insist on using the word ‘fruit’ to refer exclusively to apples, and to proceed to make claims like ‘fruit can’t be orange coloured’ that are false for some types of fruit. (Even more so when people have been using the word ‘fruit’ to refer to oranges for longer than they’ve been using it to refer to apples.) Aren’t you just making it more difficult for people to get your point that apples and oranges are different?
On your current approach, every time you make a claim about fruit, I have to try to figure out from context whether you’re really making a claim about all fruit, or just apples, or just oranges. And if I guess wrong, we just end up in a pointless and avoidable argument. Surely it’s easier to instead phrase your claims as being about apples and oranges directly when they’re intended to apply to only one type of fruit?
P.S. For the avoidance of doubt, and with apologies for obviousness: fruit=utility, apples=decision utility, oranges=substantive utility.
This doesn’t seem to me to argue in favour of using wording that’s associated with the (potentially illegitimate) superconcept to refer to one part of it. Also, the post you were responding to (conf)used both concepts of utility, so by that stage, they were already in the same discussion, even if they didn’t belong there.
Two additional things, FWIW:
(1) There’s a lot of existing literature that distinguishes between “decision utility” and “experienced utility” (where “decision utility” corresponds to preference representation) so there is an existing terminology already out there. (Although “experienced utility” doesn’t necessarily have anything to do with preference or welfare aggregation either.)
(2) I view moral philosophy as a special case of decision theory (and e.g. axiomatic approaches and other tools of decision theory have been quite useful in to moral philosophy), so to the extent that your firewall intends to cut that off, I think it’s problematic. (Not sure that’s what you intend—but it’s one interpretation of your words in this comment.) Even Harsanyi’s argument, while flawed, is interesting in this regard (it’s much more sophisticated than Phil’s post, so I’d recommend checking it out if you haven’t already.)