Hi lloydwatkin - We're following up on this issue with a support case in your organization's secret group - We'll need to take a deeper look into this to see if there is happening due to a configuration setting. A Jive Support rep is handling the investigation, and I'll be following up in this public discussion once we have a resolution in case anyone else in the Jive Community runs into the same issue.
As an update here for anyone else in the community who has the same question, based on a support case investigation around this behavior, it was found that even when Jive is configured to only show usernames, administrators who have manage permissions will be able to see the first and last name fields when looking at content or activity generated by users.
This still means that non-admins will only be able to see the user's username when using Jive.
This is the expected functionality of the system today, although I recognize that this can be confusing being that different users see different amounts of user information depending on their permissions.