[TL;DR] Even if two users had the same "display name", you can always set them appart by their USER_ID.
- - - - -
In the "IP Board" system, to access a profile the url must be:
[name_of_the_forum].com/user/[uSER_ID]-[current_name_display]
Things in bold can not be changed without main administrative access; but the part in italics can be changed by users and moderators.
After you registered your account, you got a USER_ID based on the current "ticket number" available (counted from the first to the last account ever created, included the banned ones); and set the original email of registration needed for confirmation (you can add another email as "primary means of contact" later, but the original always remains in case of a dispute).
On every profile (overview) there is a section at the right (between the number of "likes/brohofs" and "contacts/friends"); were anyone can see all name changes for that user plus the dates in between each of them [Display name history].
The USER_ID never changes, so it is posible to locate any user in order to editing links with the current new display name for statics links outside the enviroment of the forum (were they should update by default).
Since anyone can know what was the "first" display name choosed by an user (selected in the moment of creation of the account), you can always ask a moderator to rollback to it (even if ir requires editing any other user who may have "taking" such name), in order to restore yours.
SilverComet's post in Can someone take my old username if I change it? was marked as the answer