Em dashes in every other sentence. I've never seen an actual person do that. The language in general reads exactly it's written by an LLM:

"The blah blah didn't just start as blah. It started as blah..." "First came blah -- blah blah blah" "And now: blah"

It's a distinctly AI writing style. I do wonder if we'll get to a point where people start writing this way just because it's what they're used to reading. Or maybe LLMs will get better at not writing like this before that happens.