Fighting the group chat spammers is a headache, especially when they join your group back in a minute!
To forbid certain residents to join your group, use the new SmartBots feature: the blacklist. Blacklisted residents will never receive the group invitation from SmartBots-powered devices!
This allows to secure your group chat: close the enrollment of your Second Life group and use SmartBots devices to get new group members.
Read more in SmartBots documentation!