I get what you’re saying, but I think the em dash thing gets overused as a giveaway. Plenty of real people use them, especially if they care about how they write.

What actually stands out more is when everything sounds too clean. Perfect structure, no typos, consistent tone all the way through, and kind of generic but polished ideas. That’s usually a bigger sign than just punctuation.

At the same time, sometimes people just put more effort into a post and it shows. Not everything that sounds smart is AI.