Question:

Why is the username displayed differently for different users in CRM?  

Example:

For a system administrator, the username is First Name, Last Name. But, when the user logins to the system, the name is changed to Last Name, First Name.

Answer:

The reason the first name and last name appears inverted is that the locale of the user is different from the system administrator. 

Example: Vietnamese (Vietnam) uses the last name first and then the first name.

Salesforce displays the names in an order according to the Locale of the user.

The user can check the Locale under My Settings --> Personal --> Language & Time Zone --> Locale.

Related Documentation:

CRM Help Documentation: N/A