Oh, I'm so glad Judith Martin has relaxed about this one! Years back she used to be totally keen on

Dr. Angelina Breakfront
Mr. Rock Moonley

and

Mr. Oliver Trenchant
Mr. Liam Lotherington

but she did say that the proper term of address for a m/f couple who share a surname was Mr. and Mrs. Hisfirst Herfirst. (She was totes down with non m/f couples and different surnames.)

That being said she's always said that people who use etiquette to make other uncomfortable or miserable are being impolite jerks.