Or you can just go here: http://www.livejournal.com/customize/options.bml
and on Disable customized comment pages for your journal set it to "no", and the comment page will be in the same style as your journal. It's a workaround they might eventually disable though. :/

Might I add I'd be really happy if you did that because the new LJ page makes everything I type in the boxes appear at the rate of one letter per second or sometimes more, which makes long replies really frustrating. D: *kicks stupid lj*