Oh my. Although I understand, and I do truly, that the em dash might be a tell for LLMs...I have been using it for years, now, and the last time this came up on HN I understood exactly when: Mac OS makes it very easy to type the em dash. You just long press the regular -.

I don't use a Mac anymore, but the first thing I'll do on a Linux build is configure my modifier key in such a way to produce — easily.

Not to deny that discourse on the internet, and reddit of all places, might be getting infested with LLM output. I just don't think focusing on the em dash is a good strategy to predict a tell.