Miss Manners: Is noting an invitation was delivered ‘by hand’ pretentious?

DEAR MISS MANNERS: Sometimes when I receive an invitation to an event, the sender writes “By Hand” in the lower right-hand corner of the envelope. Obviously, this means that they delivered the invitation to my house themselves, without using the postal service.

Is this a true form of etiquette? I cannot find a single reference to it in any etiquette book. It seems a bit pretentious to me, and I have always wondered if, in fact, it is really correct to use the term.

GENTLE READER: Pretentious? Miss Manners would think the opposite, as it tells you that the sender made an extra effort. And also perhaps that the sender does not trust the postal service.

EAR MISS MANNERS: How do you gently decline Christmas invitations from a friend when the people they invite are all couples and the women