by Danny van Kooten on WordPress.org

What changing a username with this plugin looks like.
Change usernames of your WordPress users effectively.
This plugin allows you to change usernames of your WordPress users in an effective and safe way.
By default, WordPress itself does not allow usernames to be changed. The other plugins for changing usernames do not scale all that well for sites with a large number of users.
This plugin takes a different approach by simply enhancing the default “edit user” page and then processing the username change over AJAX, resulting in a much faster and user-friendly experience.
Danny van Kooten has been developing plugins for WordPress since version 3.0, all the way back in 2010. Read more about him on his personal website or have a look at his various other WordPress plugins.