Slightly funny story... I agree with the concept---I was mistaken (and corrected recently); and that many tools like markdown or Word treat TWO hyphens as an EN dash and to get an EM dash you need THREE!

I love abusing the semicolon, the ellipsis and the hyphen/dash(es) to indicate a mild pause when transliterating casual speech to text. To my horror, I'd been using the wrong one!