I am a Jira administrator.
On the dashboard, I activate the "configure" option.
Click on "Add a new portlet."

My user profile is now summarized on the left.
Click on "Administer User"

=> The Admnistration tab is displayed but contains only the message "The user does not exist. Please try another."

Note : profile administration works fine when reached through the "Profile" link of the top right of the screen.