Ms Kate / Mr Thomas

[Tedwonny]

I remember having learnt that Mr/ Ms... these honorifics should NOT be followed by 'first names' alone.

E.g. You can say
Ms Wallace (full name Ann Wallace) or Ms Ann Wallace BUT not Ms Wallace

However, my colleague, a well-educated native speaker of English, has time and again call others in this way. On one occasion, she called another colleague, also a native speaker of English from the UK, Ms Kate (Kate is her first name). "Ms Kate" was a bit shocked and asked 'haha did you just call me Ms Kate?'

I felt that there was something there not so obvious. Is this for humourous effect?
Are we actually allowed to say Ms Kate?

THANKS

[Raymott]

I remember having learnt that Mr/ Ms... these honorifics should NOT be followed by 'first names' alone.

E.g. You can say
Ms Wallace (full name Ann Wallace) or Ms Ann Wallace BUT not Ms Wallace

However, my colleague, a well-educated native speaker of English, has time and again call others in this way. On one occasion, she called another colleague, also a native speaker of English from the UK, Ms Kate (Kate is her first name). "Ms Kate" was a bit shocked and asked 'haha did you just call me Ms Kate?'

I felt that there was something there not so obvious. Is this for humourous effect?
Are we actually allowed to say Ms Kate?

THANKS

No, we generally do not say Ms Kate. But you will hear it occasionally - usually when simply Kate would be too informal but Ms Wallace would be too formal.
In fact I heard it a few days ago when watching YouTube, America's Got Talent. Sarah Brightman (a famous soprano) was doing a guest performance with a young contestant. Afterwards, the MC thanked "Ms Sarah" for her performance. It was also common in the past in America where black slaves would call the children of their owners Miss Scarlet, etc.

Here's the example: It occurs at 4.48. But it's worth watching the whole thing for the music. Also there is confusion on all parts about how to address the others. At 4.36, Jackie says "To be singing with the girl ... the woman ..."
Jackie Evancho & Sarah Brightman "Time to Say Goodbye" on America's Got Talent FINALE - YouTube

[Barb_D]

It's still common in the South (by people of all races) to use "Miz Kate" when just "Kate" is too informal.

Also, children throughout the country may use "Miss Patty" for a caretaker or other adult. My daughter, who is about to be 14, had a wonderful, wonderful pre-school teacher when she was 4 who was called Miss Patty. To this day, whenever we see her in town, the entire family says "Look! It's Miss Patty! How are you?" even though by now we could call her either Patty or Mrs. Whatever-her-last-name-is.

My coworker refers to me at "Miss Barb" when she talks about me to her children.

[Tedwonny]

How very interesting indeed
THANK YOU ALL!

[Rover_KE]

Say a solicitors' practice called 'Thompson and Thompson' is run by two brothers called Stephen and Michael, callers will often say 'Can I speak to Mr Stephen, please.'

Are we actually allowed to say Ms Kate?

We're allowed to say anything we want, Tedwonny, as long as it's not slanderous.

Rover