Example of swapping a display name in the PMPro emai body.

my-pmpro-email-body-swop-current-user-display-name.php

<?php
/**
 * This recipe replaces the current user's display name in an email
 * with the recipient's display name.
 *
 * This is an example of replacing text in the email body that may
 * be handy when admin is the current user that trigges a custom mail/template from
 * the administrative area and the administrator's name appeared in places in the
 * email due to missing variables passed to the email class from a custom email/template.
 *
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */

function my_pmpro_email_body_swop_current_user_display_name( $body, $email ) {
	global $current_user;
	// Get user
	$user = get_user_by( 'email', $email->email );

	// Let's check if the current user matches the recipient
	if ( $current_user->ID !== $user->ID ) {
		// replace the current user's display name with the recipient's display name.
		$body = str_replace( $current_user->display_name, $user->display_name, $body );
	}

	return $body;

}
add_filter( 'pmpro_email_body', 'my_pmpro_email_body_swop_current_user_display_name', 20, 2 );