var cfeedbase = 'http://'+window.location.hostname+'/feeds/'+$("#navbar-iframe").attr("src").match(/targetPostID=([^&]*)/)[1]+'/comments'
and change it to:
var cfeedbase = $('link[href$="comments/default"]').attr("href").split("/default")[0];
(all in one line)
The source code has been updated in the hack's article.