I get the concern, but there’s a spectrum.

Using an LLM to polish grammar vs. having it generate opinions wholesale are different things.

I'm not necessarily saying that you used an LLM, but em dashes aren't used that often when regular people are typing. I use Grammarly all the time and they've never suggested that I add an em dash, and it's often a sign of a low-effort "ask ChatGPT for a response to this comment".

Again, not necessarily saying that's what you did, just that that's the red flag.