Change user name

I want to change my user name …

but i found these words under the edit form :

Consider carefully before changing your username as frequent changes are not permitted. Changes to your username may have an affect on URLs to your profile, items or services. History of username changes will be displayed on your profile.

Please explain “may have an affect on URLs to your profile,”

yes according to my knowledge frequent changes of user name are not permitted.
you can change user name only one time.
then you have to contact support center to change your user name.