What is rationality? It's the ability to make life plans which reach your goals. Funny thing though, the INABILITY to (care about) making such plans is the defining trait of psychopaths. In other words, Narcissists qualify as rational. No wonder Narcissist shitheads like Yudkowsky go on and on and on about rational this and rational that. He's basically crowing in triumph "I am not a psychopath!!" like it's this marvelous achievement worthy of acclaim. Worthy of adulation even!
And for your information, I first heard that definition of rationality many years before I'd ever heard of Yudkowsky or even knew what Narcissism or Psychopathy were. I heard about it from a philosophy book trying to justify Good according to Evil principles. It was a disgusting exercise but for the exercise to work the disgusting fucker obviously had to admit Narcissists and Right-Wing Authoritarians. You know, to even HAVE Evil in his assumptions.
Man, it sounds so self-aggrandizing to hear "I am not a psychopath!! HAHA. IN YOUR FACE PERSON WHO ISN'T LIKE ME!"