A poster commented that he read parenthetical remarks in an old-timey voice (I’d guess the trans-Atlantic accent). I love that idea. But for me they read almost as if you’re saying them under your breath (or a character is breaking the fourth wall and talking to the camera quietly). I read them but my brain assigns them less importance.

Em-dashes keep everything on the same level of importance in my brain.

Commas don’t feel as powerful. To be fair to the comma I’d probably do this:

Em-dash matches how I speak and think: A halt, then push onto the digression stack, then pop. So I use them like that.

Edit: I accidentally used an em-dash in the word em-dash. Interestingly HN didn’t consider changing the dash to be a change in my text so didn’t update it. I had to make a separate change and take that change out for my dash change to stick.

I picked it up from Salinger. I find that if I can't eradicate parenthesis by some other means, or if it's more effort to do so than I want to spend, em-dashes usually replace them without doing any harm and aren't quite so ugly, aside from being useful in other cases. In particular, parenthesis at the end of a sentence are awful, while a single em-dash does a similar job much more neatly and looks totally natural.