Summary:
Currently, Bitbucket Cloud enforces username uniqueness across the entire platform. This causes issues for organizations whose users wish to select usernames that may already exist globally, resulting in errors such as "An account with that name already exists."

Feature Request:
Enable Atlassian organizations to allow unique usernames within their own org for Bitbucket Cloud, rather than enforcing uniqueness across all Bitbucket Cloud users. This would allow different organizations to have users with the same username, as long as they are unique within the org.

Reduces user friction and confusion during onboarding and username changes.
Aligns with expectations from enterprise customers who manage large user bases and may have overlapping naming conventions.
Improves user experience and administrative flexibility for organizations using Bitbucket Cloud.