Jesper Johansen (jayjdk)

Twitter Profile Field is a simple WordPress plugin that gives the user a new field in the profile page to add in their Twitter username.
The pluhin also provides a shortcode which allows authors to display their, or others, Twitter usernames, optionally with a link, in posts, pages, and text widgets.

Twitter Profile Field

Adds an additional field to the user profile page where the user can enter their Twitter username.

wpyb

To prevent that usernames are publically visible, the username in the author’s permalink is replaced with the author’s ID. 
In case the page is invoked with the default permalink structure, it is displayed “Page not found”.
Additionally it is possible to modify the author base. It is recommended to make use of this plugin to change it, but it also works with other plugins that have the functionality to customize the author base.

Change Author Link Structure

To prevent that usernames are publically visible, the username in the author's permalink is replaced with the author's ID.

Twitter Profile Field vs Change Author Link Structure