I18n: Introduce more translator comments for strings that contain placeholders but don't have an accompanying translator comment.

See #38882

Built from https://develop.svn.wordpress.org/trunk@39326


git-svn-id: http://core.svn.wordpress.org/trunk@39266 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-mail.php

@@ -118,6 +118,7 @@ for ( $i = 1; $i <= $count; $i++ ) {
 					$author = trim($line);
 				$author = sanitize_email($author);
 				if ( is_email($author) ) {
+					/* translators: Post author email address */
 					echo '<p>' . sprintf(__('Author is %s'), $author) . '</p>';
 					$userdata = get_user_by('email', $author);
 					if ( ! empty( $userdata ) ) {