I think that part of this advice can be restated as "every character must think themselves the protagonist of their own lives" which I think I remember Orson Scott Card giving; though Eliezer's advice more explicitly focuses on how this affects their models of the universe.

A decade back, I was conciously attempting to use OSC's (if that's who I got it from) advice in a piece of Gargoyles fanfiction "Names and Forms" set in mythological-era Crete. In that story I had a character who saw everything through the prism of ethnic relations (Eteocretans vs Achaeans vs Lycians), and there's another who because of his partly-divine heritage couldn't help thinking about how gods and human and gargoyles interact with each other, and Daedalus in his cameo appearance treated everything as just puzzles to be solved, whether it's a case of murder or a case of how-to-build-a-folding-chair... (Note: It's not a piece of rationalist fanfiction, nor does it involve anything particularly relevant to LessWrong-related topics.)