I suspect that as the game matures, an informal set of courtesies will grow up around the usage of FC chat and LS chat. These types of things tend to be rather organic, so I can only guess, but I suspect something like the following will be established naturally by the players:
  • FC chat will be used exclusively for event discussion and FC based notices.
  • LS chat will be used for general socializing.
  • Any FC will have an associated LS for non-event related chat.

This way, you can stay in touch with people you don't do events with normally, since LSs will have overlap.