Most AI generated text doesn't seem to have spaces around the em dashes. I've been using that as a subtle distinguishing marker; as both forms are considered grammatically correct.

tldr: use spaces around em dashes

Huh, I've observed the opposite, AI-generated text uses spaces most of the time. Might depend on language? Style guides I use (like Chicago) don't put spaces between em dashes so those always stand out immediately to me.

The whole point is not to change one's writing style simply because it has been associated with LLMs. Don't feed the paranoia!

The typography I learned insists on no spaces