I apoloized for the poor quality -screen cap I saved in album so I could post it here. This is all I have when I go to edit my profile details. There is no custom usertitle on the menu when I click my avatar.
It looks like with the way the forum settings are set up at present only staff can adjust their user titles. The others posting with custom usertitles under their names, may have done it under older software. It has not been enabled for members under Xenforo.
On the other Xenforo sites I am on - and I am on 3 others, this feature is enabled for members.