lj autoupdate – comments link back

I’m using the LJ Autoupdate Hack as described at:
https://weblogtoolscollection.com/b2-img/ljautoupdate12.txt
When I make a post to my WP blog at https://www.joeclark.net, it posts automatically to my Livejournal. I want to also add a phrase to each LJ entry that says “view comments at joeclark.net” and links back to that entry’s permalink.
So after the lines:
$content = stripslashes(stripslashes($content));
$content = convert_smilies($content);
$content = convert_chars($content, 'html');
I added:
$content .= 'comment on joeclark.net';
Which you think would do the trick, but it doesn’t. $post_ID perhaps is not the variable to use, or my PHP syntax is wrong. The link outputs to Livejournal fine, but there’s no number in the URL. Any help please???