I created a Farklet (drag the bookmarklet to your bookmarks toolbar). Its purpose is to sort, whenever possible, threads in Fark.com by the ammount of people commenting in them.
FARK.user.js, a userscript, is also available… It runs when the page has loaded, and it only runs in the sections which are sortable.
Here is the Farklet.js (the ‘source code’). This script is provided to you under the terms of the GNU GPL.
Here is the Fark Thread announcing the script