Joel is a great guy who apparently loves the em dash. Personally, I find them particularly annoying, pedantic, and always have. Just use a comma, when I'm reading something with an em dash it's always unclear to me exactly how long I should pause, especially when reading aloud..., how dramatic...?!

I use a plugin[1] on my blog that automatically translates ‘--‘ or ‘---‘ into em or en dashes. I did not see it coming that now my articles will look AI-written :p

Edit: just discovered iOS keyboard input also does this when you type multiple hyphens

1 - https://daringfireball.net/projects/smartypants/

a short dash - with spaces around it - is clearly a punction mark, not a word-joiner. what nonsense! anyway, you can not expect everyone to use 4 or more different key combinations depending what style they want. the only solution is to make firefox, word, etc choose the right dash for word-joining, punctuation, minus, number ranges, etc. somewhat similar to how they can choose the width of spaces in justified text.

Yeah I never used them before I worked at the FSF. The FSF used the Chicago Manual of Style.