So, when we're distinguishing "optimal car-buying" from "rational car-buying," is the point that using the word "rational" is somehow wrong and distorts or confuses the intended message? Or is really just that we want to save the word for when we need it most, so as to safeguard against death-spiraling around "rationality"? I'm not trying to suggest that the latter wouldn't be a good enough reason, but I'm trying to figure out if Eliezer's point is about being precise with this concept on a substantive level, or more about community norms, rhetorical efficacy, and sanity prophylactics. The last sentence of the OP suggests the latter is at least in play, but I'm trying to figure out whether this issue suggests some problem with what we mean by the word in the first place.