From what I've seen and read, a Display Representation, like energy, cannot be created or destroyed. Ok, but can it at least be renamed?
Depends on the Display Representation [DR]. There are "core" DR's that are defined "in the code" that can not be deleted or, so far as I know, be renamed.
You can not create an entirely new DR, but you can make a copy of a DR and rename the copy. Some of the DR's that are in the out-of-the-box Display System are not "core" DR's, but are copies of core DR's and can be deleted and/or renamed. In order to delete the DR, you will need to make certain it is not being referenced anywhere in the file, at the drawing-default level in a Display Representation Set, or in any style- or object-level overrides.