Your comments
https://medium.com/swlh/the-surprisingly-simple-thing-slack-got-wrong-b16f489395e#.89ksvzbci This view is shared by a lot of people. It's somewhat different than my other suggestion that would allow a user to participate across many organizations (teams and forums) from within their own personal organization. This would be a good start @MikeB globally
Customer support service by UserEcho
https://medium.com/swlh/the-surprisingly-simple-thing-slack-got-wrong-b16f489395e#.89ksvzbci
Starting with single account and building upon that concept