No offense taken, but realize that good number of us folks who have learned English as a second language have been taught in this way (especially in an academic setting). LLMs' writing are like that of people, not the other way around.

wouldn't say that... they're very distinctly not like people, that's (part of) the problem. But I don't think the difference is measured exactly in the choices of words and punctuation. It's more like... you can tell, reading AI writing, that it's not "sincere"; no person would want to say what the AI is saying, because it feels fake and disingenuous. The phrases and em dashes and whatever else are just the method for this effect. Real people use the same phrases but with real intent to communicate behind them, and the result is different in a way that is curiously easy to detect.