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!

i think the genie is out of the box; but i stand with your sentiment!

The typography I learned insists on no spaces