Add standard WP password hint to checkout right below account creation fields.
<?php
/*
 * Plugin Name: Easy Digital Downloads - Add Password Hint
 * Description: Add standard WP password hint to checkout right below account creation fields.
 * Author: Easy Digital Downloads
 * Author URI: https://easydigitaldownloads.com/
 * Version: 1.0
 */

function pd_add_standard_wp_password_hint() {
	?>

	<p id="edd-password-hint-wrap">
		<?php echo wp_get_password_hint(); ?>
	</p>

	<?php
}
add_action( 'edd_register_account_fields_after', 'pd_add_standard_wp_password_hint', 10, 2 );
To implement this snippet on your site, create a brand new, empty WordPress plugin and paste the above code inside.