My name is not particularly common so I don’t know if the shortened version is common among those with my name or not. I have only met two other people with my name, both males and both significantly younger than me. I have not asked T to use the shortened version of my name. My last T just did, then caught herself and asked. Most of my T’s have just used it. It isn’t a big deal to me with T as he tends to be very formal despite being very warm and approachable. It might be a bigger deal with me and art T though… I think with her style my shortened name just fits better… then we will see how they work it out when they meet and/or all three of us are in a room together.
Honestly it wouldn’t surprise me if using formal names isn’t a way my T keeps the therapeutic space and would be a boundary unless a client was adamant.