Love them or loathe them, the use of designatory letters (or post-nominal letters, also called post-nominal initials or post-nominal titles) is entirely down to the individual and perhaps their use is not as simple as one might assume.
Designatory letters are letters placed after the name of a person to indicate that the individual holds a position, educational degree, accreditation, office, or honour. In my instance, MCIM, of which I’m very proud, for a whole host of reasons which I generally don’t divulge!
I recently had the misfortune to listen to someone at a conference who, after identifying two people in the room with the MCIM title, not only totally mis-represented the qualification once, but three times!
So the moral of this story is, whether you love them or loathe them, don’t criticise their use or validity without knowing what they are, what they mean and how they are obtained and, perhaps even more importantly, the story behind the individual first.