Comic book letterer extraordinaire Todd Klein combines two of my favorite things—comics and typography—in his fantastic blog. His latest entry answers a reader's question regarding dots, dashes, em-dashes, ellipses, and underlining (“We NEVER underline in comics!”):
...why is the double hyphen still used in comic book lettering when the en-dash (or em-dash) is so much more elegant? I can’t see any reason for it other than “that’s the way it’s always been done.” As the source of all things lettering, I hope you would be able to tell me.
He then proceeds to explain at length, in a fascinating article. Check it out here.