Show membership level next to comments with Paid Memberships Pro.

my_comment_author_show_membership_level.php

/**
 * Show membership level next to comments.
 * This gist will work with PMPro and most WP themes.
 * Add this code into a custom plugin. https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */
function my_comment_author_show_membership_level( $author_text, $comment_ID ) {
	$email = get_comment_author_email( $comment_ID );
	if( empty( $email ) ) {
		return $author_text;
	}

	$user = get_user_by( 'email', $email );
	if( empty( $user ) ) {
		return $author_text;
	}

	if( function_exists( 'pmpro_hasMembershipLevel' ) && pmpro_hasMembershipLevel( NULL, $user->ID ) ) {
		$level = pmpro_getMembershipLevelForUser( $user->ID );
		$author_text = $author_text . ' (' . $level->name . ')';
	}

	return $author_text;
}
add_filter( 'comment_author', 'my_comment_author_show_membership_level', 10, 2 );

This recipe is included in the blog post on "Show a Member’s Level Name in Post Comments" at Paid Memberships Pro here: https://www.paidmembershipspro.com/show-a-members-level-name-in-post-comments/