Display name publicly as doesn't update menu correctly

[stuartshields]

To reproduce

1. Go to Users
2. Select User
3. Update either First name, Last name or Nickname
4. Click on Display name publicly as - you'll see the new items added here
5. Go back and update either First name, Last name or Nickname
6. Click on Display name publicly as - you'll see the new items added here plus the previous updates you made
7. Click on any of the items in Display name publicly as that aren't currently in the First name, Last name or Nickname
8. Click save
9. Display name publicly as will show the save result of them item, even though it doesn't exist.

Results
The Display name publicly as displays an item that isn't not in a saved field

Expected result
Display name publicly as should update the menu when ever a new item is added in First name, Last name or Nickname keeping both the newly entered item and the original last save item. Currently it will continue to show new items in the dropdown menu until saved.

Versions tested
4.2.2, 4.2.3 and 4.3 beta 4

[stuartshields]

All items are saved in the select menu

[stuartshields]

Saved item isn't in First name, Last name or Nickname fields

[netweb]

Thanks for the ticket Stuart

Upon a bit of research this is actually expected behaviour, it was implemented in r20964.

"Do not clear the old values in "Display name publicly as" drop-down on the user profile screen, append new values there when the user changes any of the name fields"

For more context please see the extra discussion #20747