John Gruber on the rise in the use of *asterisks* for emphasis
in the plaintext age: "Neither appeared in print until the mid-’60s, when *sigh* began appearing. But *cough* doesn’t appear until 1987. Both though, exploded in usage starting in 1997, and have risen steadily ever since. So I think I’m correct that this use of asterisks has been largely driven by Internet punctuation idioms."