Sorry, I was unclear. What I'm saying is that the NEGATIVE sign doesn't work that way :) There's an include, but no exclude. I'd open trac and put this in as a request to add to WP.
This code (which is from the link I gave you) skips category 112, so I suspect you could re-jigger it to have it check for in-post instead:
<?php
global $comment; if ( $comments = $wpdb->get_results("SELECT comment_author, comment_author_url, comment_ID, comment_post_ID FROM $wpdb->comments WHERE comment_approved='1' AND comment_type='' ORDER BY comment_date_gmt DESC LIMIT 10") ) : ?>
<ul>
<?php foreach ($comments as $comment) {
if (in_category( '112', $comment->comment_post_ID ){
continue;
}
echo '<li>' . sprintf('%s <span style="text-transform: lowercase;">on </span>%s', get_comment_author_link(), '<a href="'. get_permalink($comment->comment_post_ID) . '#comment-' . $comment->comment_ID . '">' . get_the_title($comment->comment_post_ID) . '</a>');
echo '</li>'; } ?>
</ul>
<?php endif; ?>