Markdown Reference User Autocomplete

When I am editing an issue, I want to CC a particular user in Gitlab instance. I can do the @user and it works. Although if I don’t know the username of the user off the top of my head and the user is not in the project the Autocomplete doesn’t help me in trying to find the user.

Could it be possible to include in the Autocomplete, users that have the correct permissions to view the issue, also be included in the Autocomplete?