I loved em-dashes --- I still do (as you can see, I'm partial to AP style ;)) But most people never understood the difference between hyphens, en-dashes and em-dashes in the first place. Or that The King's English uses en-dashes where US English uses em-dashes. Merriam-Webster has a short and amusing -- to me -- article on this topic [1]. So all kinds of "dashes" are rolled into the "em-dash is an AI tell" hysteria.

That LLMs use them all the time is also a good indicator that there are alot to be found in the training material.

[1] https://www.merriam-webster.com/grammar/how-to-use-and-under...