Insight Objects can have user objects as attributes. If more than two users have the same username, it becomes confusing when choosing the user attribute.

Insight does allow duplicate usernames, unlike Jira.

In Jira, the user drop-down lists names with email. Similarly, it should have a better option to display usernames in the insight attribute drop-down. 

Workaround: When editing an object in the Object schema view, the user attribute dropdown displays "username - email@mail.com", making it easier to differentiate the users. When editing in the Object view, only the usernames are displayed in the dropdown.