[defgeneric]

I'm seeing this reaction a lot from younger people (say, roughly under 25). And it's a shame this new suspicion has now translated into a prohibition on the use of dashes.

[kazinator]

I use three hyphens. In my case, I picked it up from Knuth's TeX many years ago; it's a lexical notation which typesets to a proper em dash.

Three hyphens---it looks good! When I use three hyphens, it's like I dropped three fast rounds out of a magazine. It demands attention.

[almosthere]

It's comical too because the only reason AI uses emdashes is because it was so common before AI.

[kazinator]

It's utterly uncommon in the kind of casual writing for which people are using AI, that's why it got noticed. Social media posts, blogs, ...

AI almost certainly picked it up mainly from typeset documents, like PDF papers.

It's also possible that some models have a tokenizing rule for recognizing faked-out em-dashes made of hyphens and turning them into real em-dash tokens.

[protontypes]

Maybe because the em dash is not on the keyboard of most people? It is not about the dash, but about the long em dash.

[int_19h]

It's very easy to type on macOS, not to mention auto-substitution that many apps have (and these days this extends to web browsers).