I would recommend against someone with an honorary doctorate using "Dr." in the way RMS does. Even for those who have an actual Ph.D. are better off not saying

I would recommend against someone with an honorary doctorate using "Dr." in the way RMS does. Even for those who have an actual Ph.D. are better off not saying "Dr.". I do have "Ph.D" on my business cards but haven't handed one out in years (mine's from UC Berkeley, 1993). I never call myself "Doctor", that just seems weird. But it may be appropriate for an academic in an academic setting.