Some of the strings in the wp-commentsrss2.php are not internationalized.
Line 23 :
<title><?php if (is_single() || is_page()) { echo "Comments on: "; the_title_rss(); } else { bloginfo_rss("name"); echo " Comments"; } ?></title>
Line54 :
<title>by: <?php comment_author_rss() ?></title>
Line 61 :
<description>Protected Comments: Please enter your password to view comments.</description>
Seems like they should read :
Line 23 :
<title><?php if (is_single() || is_page()) { echo __("Comments on: "); the_title_rss(); } else { bloginfo_rss("name"); echo __(" Comments"); } ?></title>
Line54 :
<title><?php _e("by:"); comment_author_rss() ?></title>
Line 61 :
<description><?php _e("Protected Comments: Please enter your password to view comments." ?></description>
