Please note that in post #49, I said specifically that “I’m aware that some of these middle initials were made up when the person entered their profession and needed an initial.” I said that specifically because I knew very well where the middle initial in the names Ulysses S. Grant, Harry S. Truman, Michael J. Fox, and J. K. Rowling came from. You’re not telling me anything new.
Please note that I specifically talked about the use of initials in the U.K. in post #49. Northern Ireland was in 1898 part of the U.K. and still is part of it. Of course I knew where Lewis was born.
It may be true that it’s no longer as common to refer to authors, etc. by just the initials of their first and middle names. A few British authors born in 1930 or later who use initials for those names are A. N. Wilson, A. S. Byatt, D. M. Thomas, E. L. James, J. G. Ballard, and J. G. Farrell. So while it may be less common, it hasn’t entirely disappeared. I should note though that there are some American authors, etc. who use initials for all of their first and middle names, so some Americans do it too.
You didn’t say specifically that Rowling was one of the people that didn’t really have the middle name Katherine, and while I think it’s relatively well-known that she didn’t, it might not be so well known that a) she didn’t have a middle name at all and b) that is uncommon in the UK and becoming ever less common - like I said, I have no cite for that, but if multiple middle names are increasing in popularity it seems reasonable to assume that not giving a middle name at all is also declining.
It’s just an on-topic comment, not an argument or anything relating to you personally.
My kidlets get one name picked by a parent, one middle name picked by the other parent, second middle name that is my last name (I did not change my name on marriage) and their last name that matches my husband’s. I used my “picks” to bring in Irish names in remembrance of that side of my family. I think he threw darts.
In Catholic culture we take another name at our confirmation and insert it between our middle and family name. I’ve never heard anyone identify themselves with it in the secular world, but it is often used within the family. It’s customary to choose the name of an admired saint that the confirmand would like to have as a patron. My wife is French and I’m of Irish origin. Our two oldest are twins. Our son took the name of the Irish saint, Oliver Plunkett. Hence, he has two additional names. Our daughter took the name of the French saint, Therese de l’enfant Jesus. She, accordingly, has a rather interesting insertion between her middle name and family name which gives her the happy opportunity to explain when asked. Our youngest took the name, Jean d’Arc.
Many people with Spanish heritage have first name, middle name, father’s surname and mother’s surname, in that order. (Not sure where the confirmation name goes if Catholic.) This is very common in Chile and the Philippines.
My youngest has two middle names. First name was chosen by my wife. The “middle-1” name is her mother’s name. The “middle-2” name is a mashup of the names she was given by the orphanage (though not the family name, because every baby at the orphanage was just given the family name “Long”).