The only people still using em-dashes are those who think it's somehow a signal of high intellect rather than being (extremely) behind the times. Case in point: this exact comment section where you see it with ~10000x the frequency of standard human writing, or even the average HN thread.
Just makes me roll my eyes really seeing a human use an em-dash. We've in the age of informality, and at least for me personally I've definitely filed the em-dash away as "a near guarantee the text was written by a machine". No matter how much and perhaps especially because HN commentators are coming out of the woodworks to insist they've been using it daily for years.