You may notice that he didn't use the double or triple hyphen annotations either - which is usually only used in contexts such as latex, where a post-processor goes over the output for display.
I like to use a lazy variant -- it's not a double dash, or a weirdly written plus, it's a an em-dash that says "I don't even have this key on my keyboard, are you actually using alt-codes or what am I missing?". Not with a shout or a whisper, but with the quiet courage of just being -- but not an incomplete representation of a whole, but rather the fullness of that very distillation of honest, simple pragmatism. Not less, just different.
- = hyphen
-- = n-dash
--- = m-dash