Note: I searched for this bug, but they are all old with a lack of attension from the community, and don't completely explain the bug and why it's bad, so I'm posting this with more information on it.
At the moment, the name tag of a player cannot be changed without changing the name of the player. There are a few problems with this dependency. Firstly, I cannot change the player's name without their skin changing. Another thing is changing the color of a name. If I cant change the color of a player's name tag if his name is 15/16 letters long. If a player's name is "OP", and I try to color his name the end of his actual name will be cut off and his name will become "§cABCDEFGHIJKLMN", and since his name is different now, his skin will change.
If a name tag needs to stay the same as a player's name, then I think the name should at least be able to be longer to allow for name tag coloration without players' names being changed.
Comments 3
It's a bug (or unexpected behavior) in the sense that players with 15/16 letter usernames have their name cut off when their name is colored, resulting their skin and username changing.
This is not a bug, but a feature request, and should be posted on the MC forums here.