"It's rational to vote for Party X" deflates to "It's optimal to vote for Party X" or just "I think you should vote for Party X".

I'm starting to get very confused about what Eliezer means by "deflates to". I thought he meant "has the same meaning as" or "conveys the same meaning as", but now I think maybe he means "most of the time when you want to use the former, you should use the latter instead". Sorry if I'm still stuck on the by-now-not-quite-central topic of semantics, but I don't see how "rational" has the same meaning as "should", either according to my own understanding, or according to definitions given by Eliezer in the past. (My understanding is that "should" conveys some hard-to-define sense of normativity, whereas "rationality" is a subset of normativity that seems more objective than the other parts, which we usually call "morality".)