Please don't confuse Username and Nicename. Those are not the same.
Nicenames are used for user @mentioning and in your profile URL. So again, this is the nicename, not username.
You can enable the wpDiscuz mentioning feature in the Dashboard > wpDiscuz > Settings > Subscription and User Following admin page.
For more information, visit: https://wpdiscuz.com/docs/wpdiscuz-7/plugin-settings/subscription-and-user-following/#enable-user-mentioning
Important: To display the nicenames, insert the following code in your WordPress active theme's functions.php file:
add_filter("wpdiscuz_show_nicename", "__return_true");
For guidance on adding custom code in WordPress without disrupting your site, refer to this article:: https://www.wpbeginner.com/plugins/how-to-easily-add-custom-code-in-wordpress-without-breaking-your-site/
In case you want to say thank you! 🙂
We'd really appreciate if you leave a good review on the plugin page.
This is the best way to say thank you to this project and the support team.