PLEASE NO!  It will be a nightmare for teachers and for you to police.   If they are playing the game, there should be NO time to chat.  I have been warning my parents for the last few years to be aware of multiple sites where students say they are working on FIM but are switching easily between sites so they can chat or play other games(while telling their parents that they are spending time on FIM and homework).  If a chat site is attached to FIM, it will be used for many things and very little of it will be math.  I have a hard time understanding all the votes for this and am wondering if these are truly teachers voting or if they simply haven't been using the game to its full potential or haven't been on chat sites.  I know my parents will be worried if there is a chat site attached as many of them do not allow their children on these.