In article ,
Not the Karl Orff wrote:

To what extent is it permitted for an airline company to sell "first
class discounted" tickets to passengers that will eventually travel in
economy class or enhanced economy ?

not usual but then you are flying on an unusual airline!

Air France is not all that unusual, not since they stopped their
Concorde service

AOM by any chance?

Hasn't AOM merged with Air Liberte and then liquidated after some kind
of protracted bankruptcy process a few years ago?