I fixed this in my RSS comments file directly. I believe a request exists for this in trac.wordpress.org; and if so it should get rolled into the next release.
Line 52 of wp-commentsrs2.php, change from
<title>by: <?php comment_author_rss() ?></title>
to
<title>Comment on <?php the_title_rss($comment->comment_post_ID); ?> by: <?php comment_author_rss() ?></title>
Oh, I forgot that that won’t be sufficient. the_title_rss() needs to also be changed:
/wp-includes/feed-functions.php, line 12:
ORIGINAL:
function the_title_rss() {
$title = get_the_title();
$title = apply_filters('the_title', $title);
$title = apply_filters('the_title_rss', $title);
echo $title;
}
CHANGE TO:
function the_title_rss($id = 0) {
$title = get_the_title($id);
$title = apply_filters('the_title', $title);
$title = apply_filters('the_title_rss', $title);
echo $title;
}
