So, the question becomes, how do you recognize "rationalist" stories in non-fan-fic form? Is it simply the presence of show-your-work-smart characters? Is simply behaving rationally sufficient?

Every genre has a theme...romance, adventure, etc.

I'd say the difference between "rationalists" stories and "non-rationalist" stories lies in the moral of the story, of the lessons the story teaches you.

I don't think it's a genre in the same way romance or adventure are. It's more of a qualifier. You can have rationalist romance novels or rationalist adventure movies.

Although you could argue that it is a genre. While discussions about "genre" are often hard, since people don't tend to agree on what makes something a genre.

But rationalist fiction already has a couple of genre conventions, such as no-one being allowed to hold the idiot ball or teaching the audience new and useful techniques for overcoming challenges.