So many, many, many moons ago (over seven years!) I posted about a greasemonkey script that provided a comment killfile. (See that page if you're unfamiliar with the concept)
It was popular and useful for a while, but mostly succumbed to bit rot while I was at Google and I hadn't had a chance to play with the code in a modern web environment until recently.
I now have an experimental version of my old killfile redone as a chrome extension, and am looking for a few early tester volunteers to find out the places it should work that it doesn't yet. I'm also interested to see if the chrome sync stuff works for people who aren't me. (in theory, all your chrome devices should know about who you've tagged as a troll)
Now I'm providing even less support for this version than I provided for that greasemonkey script, so don't even bother asking unless you feel comfortable following the steps on this page under the heading "Steps on adding extensions from other websites".
But if you'd like to test this thing send me an email at martin -at- snowplow -dot- org.