Depending on group membership users may (or may not) see users in their own or in other groups in the People Directory.
- Internal people should be able to see all users (from their department and/or project group) as well as all customers that they are responsible for / ideally grouped per company/department/...
- External users (customers) from company XYZ should be able to see (some) internal users (i.e. those responsible for their project), in addition all users from their own organization (members in the group XYZ) and possibly some users from another company that is utilizing the same product.
Above could be solved by smart grouping of people, provided that the access to the People Directory is "better" configurable.
Note: The "Shared Mode" setting in the General Configuration does not solve the issue - this is an all-or-nothing approach, it would be highly desirable to have a fine-grained controlled access to the People Directory in one of the future Confluence releases.