While grouping has been implemented, the UI is not quite complete yet. Here are the commands to manage groups and syndicates (guilds):
/w [name] - private message
/p [message]- message to group
/invite [name], /inv [name] - invite to group
/kick [name] - kick from group
/leave - leave the group
/ginvite [name] - invite to syndicate
/gquit - quit from syndicate
/gdisband - disband your syndicate
/gkick [name] - kick from syndicate
/g [message] - message to syndicate
O opens the syndicate menu (also a work in progress).
Last but not least, not quite grouping but important:
/unstuck - reset position for those moments when something breaks (don't forget to file a report!)