How can I stop comments from indenting?

Hopefully this won't take up too much of your time!

I've installed this theme and tinkered a bit with it - love it to bits - but I would really like to make a custom forum layout, and for that I want to stop indentation in comments. Any idea how I can do that here, or pointers? I've really tried to find my own way but I'm having a hard time :) Even with firebug!

Thanks in advance,