I completely understand that character names serve no purpose, and that unlike games like PoE, names can be the same across accounts. It is purely a cosmetic/QoL thing to be able to change a characters name.
That said, I really wish I could. I enjoy having character names that fit the build im using for them, but sometimes I level up a character and decide i want to change builds, but then the characters name no longer matches. I would even happily pay some real money to get to change characters names, treating it as the same principal as paying for cosmetics. Please at some point add this to the game, even if it cost ingame gold or a little bit of real life money.