Syntax:  .hide   or   .hide <user>

Results:  Turns you invis when used without name.  When used with a user's 
          name behind it, turns that user invisible.  To return to being
          visible, type .hide again.

   Note:  You can only hide or unhide another user when they are
          capable of doing it themselves. Reason being, if you make them
          invis and then you log off, how do they become visible again?
          They're up the creek without a paddle. :-)