Wait, seriously? That sounds like a gross misuse of terminology, since "utilitarianism" is an established term in philosophy that specifically talks about maximising some external aggregative value such as "total happiness", or "total pleasure minus suffering".

To an untrained reader, this would seem as if you'd just repeated in different words what I said ;)

I don't see "utilitarianism" itself used all that often, to be honest. I've seen the phrase "in utilitarian fashion", usually referring more to my description than the traditional meaning you've described.

"Utility function", on the other hand, gets thrown around a lot with a very general meaning that seems to be "If there's something you'd prefer than maximizing your utility function, then that wasn't your real utility function".

I think one important source of confusion is that LWers routinely use concepts that were popularized or even invented by primary utilitarians (or so I'm guessing, since these concepts come up on the wikipedia page for utilitarianism), and then some reader assumes they're using utilitarianism as a whole in their thinking, and the discussion drifts from "utility" and "utility function" to "in utilitarian fashion" and "utility is generally applicable" to "utilitarianism is true" and "(global, single-variable-per-population) utility is the only thing of moral value in the universe!".