what I do find rude is when someone I do not know addresses me by my first name without first asking my permission to do so!
Now, how's that for being a stuffy old phart?

Now, this is going back over 35 years, when I was actually interested in etiquette, but, if the Emily Post part of my brain still has anything left there, I remember reading that once you're over 40, you can address people by their first names. I could have an error in what I remember having read, but that's how the "rule" has remained fixed in my head, one that I found impossible to follow once reaching 40. Mr. Wallack, my beloved strings teacher, I called Mr. Wallack though I was 50 even though he kept saying, "Call me Norman!!"

Bowing regards,
Wordwind