That's a "throwback" to the many years I've spent on Usenet.  The  is one of several abbreviations that are used there.  It signifies a grin.  For example, there is the regular grin:    and then there is the wide grin:  <<>>.  It's a quick way to show someone that you are kidding with them, or that your words are "tongue in cheek".  The  predates even smilies.  Best of everything to you and yours! –  ( CLIMAX )