add_filter("wpdiscuz_comment_author", 'custom_comment_author', 10, 2 );
function custom_comment_author( $authorName, $commentID ) {

$comment = get_comment( $commentID );
$user = get_user_by( 'email', $comment->comment_author_email );

if( !$user ):

return $authorName;

else:

$firstname = get_user_meta( $user->ID, 'first_name', true );
$lastname = get_user_meta( $user->ID, 'last_name', true );

if( empty( $firstname ) OR empty( $lastname ) ):

return $authorName;

else:

return $firstname . ' ' . $lastname;

endif;

endif;

}

You should change the value of the "Display name publicly as" option. Navigate to Dashboard > Users admin page edit the user profile and change the value of the option. 

The plugin just updates the first and last names, but not the value of the "Display name publicly as" option. 

Thank you so much for your great plugin.

But I have a issue, pls help me out.

Is there anyway to show the name of author comment as display name instead of their mail'sname

as below