my original words:
Microsoft computer name is the computer's ID,and is equal with full name.
System user name is the computer's control account's ID,but full name is similar with describtion for the current account ID that it can be any charct you want to be.
The name of the computer is the ID of the computer, the full name is the same as the computer ID.
The user name of the operating system is the computer's control account ID.
But the user full name is similar to the user name description, you can modify any characters you want, will not have an impact on the system.