The community member who created the post wants to be able to specify whether a user can belong to only one organization or multiple organizations. The first comment asks the community member to explain their use case further, noting that users will always belong to a default organization. The second comment indicates that the community member's use case does not require users to be part of multiple organizations, as this can cause issues when a registered user tries to register again from a screen made for another organization. The third comment acknowledges the community member's concern and suggests exploring the mix of org_code and adv orgs features to potentially solve this issue.
I've talked once with Oli about that. It's just like for my use case I don't need nor want a user to be part of multiple org as it will happen when a already registered user will try to register again from a screen made for another org