from which much of morality can be systematically derived
Not all of it, though, because you still need some "core" or "terminal" values that you use do decide what counts as a win. In fact, all the stuff that's derived from game theory seems to be what we call instrumental values, and they're in some sense the less important ones, the larger portion of the arguments about morality end up being about those "terminal" values, if they even exist.
You are talking about different things Dolores is talking about "why should I cooperate instead of cheating" kind of morality. You on the other hand are talking about meta-ethics, that is what is the meaning of right and wrong, what is value etc.
Do you believe in an objective morality capable of being scientifically investigated (a la Sam Harris *or others*), or are you a moral nihilist/relativist? There seems to be some division on this point. I would have thought Less Wrong to be well in the former camp.
Edit: There seems to be some confusion - when I say "an objective morality capable of being scientifically investigated (a la Sam Harris *or others*)" - I do NOT mean something like a "one true, universal, metaphysical morality for all mind-designs" like the Socratic/Platonic Form of Good or any such nonsense. I just mean something in reality that's mind-independent - in the sense that it is hard-wired, e.g. by evolution, and thus independent/prior to any later knowledge or cognitive content - and thus can be investigated scientifically. It is a definite "is" from which we can make true "ought" statements relative to that "is". See drethelin's comment and my analysis of Clippy.