@andre-clemente,
Please see the issue described below.
WordPress has three different names for Users:
- Username (Login) – Being used for website authorization (login, sign-in) action
- Display Name – Other users and guests see in user profile details and next to user posts (post author name).
- Nicename – Unique name
After a regular user registration process, Username, Display Name, and Nicename are set the same. For example, If you register a user with “Martin59” Username your user names look like this:
- Username – Martin59
- Display Name – Martin59
- Nicename – martin59
The wpDiscuz User & Comment Mentioning addon uses WordPress nicename. The filed is being generated based on the username (as mentioned above). In your case, the nicename is matched with the username, and as a value of the username is set the email address. So you see the email as a value of the mentioning nickname.
You can find and change the nickname filed's value in wp_users table. Just find the users_nicename column.
This article may be helpful for you: https://wordpress.2bearstudio.com/batch-rename-wordpress-user_nicename/
