Ha! Perhaps I should have said "when/where." I was specifically taught the rule was optional. A brief perusal of the Wikipedia article on the subject helps me understand that it should have been taught as "situational." And I learned about Sir Roger Casement's "hanged on a comma," so that's cool.

Since it took me a minute to track down, here's the short of it so that I don't accidentally nerd-snipe anyone:

http://web.archive.org/web/20110820004307/https://www.funtri...