Okay, seriously: I've noticed this for quite a long time, and have even become accustomed to doing it myself -- but what's the history behind the practice of enclosing a phrase in asterisks to indicate an action (real or imaginary) on the part of the poster, or even just some kind of action in general?
In all fairness, this isn't something that I absolutely have to know; but I am rather curious as to how it all got started.