Unsubscribe link not working?

Hello,
I was testing the email notifications and I noticed that the unsubscribe link

<?php echo $unsubscribe;?>

just generate a link to my site homepage. Is the unsubscription happening in background? I do not see any confirmation message either... but maybe it doesn't work because I am posting comments under a test article which I am also the author of (I tested posting a comment and checking the "subscribe me for notifications" box).

Thanks