If you invite someone standing right next to you to your fireteam, them accepting the invite shouldn't kick them to orbit before bringing them back down. If you kick someone from your fireteam (or they leave on their own) in Patrol or in a Social Space, it shouldn't kick that person to orbit by default, they should be allowed to remain in the instance. It's stupid, and it would make organizing things like EP so much easier if it just didn't happen.