I remember hearing that gays use a special code to display what they like, and whether they like do do it, or have it done to them.

A lengthy trawl round some fairly unsavoury websites today has confirmed this to be the case! It boils down to what colour your handkerchief is, and which pocket it's in. There appear to be about 50 different hanky colour codes (eg. red & white = shaving, olive = uniform, fuscia = spanking), and handkerchief placement says whether you're an -er or an -ee. (e.g. left pocket = spanker, right pocket = spankee)

So how did this complicated protocol get started? Is there an underground RFC system?