In order to change the way that users appear inside the platform, you can go to the 'System settings' -> 'Users' section (1) and move to the Advanced tab (2).  

Through the Username format option (3) you can choose to show their login only or many other alternatives (only last name, last name and first name, last name and the first letter of the first name and any other combination of these).

You can use the following variables:

• #name# for the First name
• #surname# for the Last name
• #login# for the username (login)
• #type# for the user type
• #n# for the First name's initial