CSS and Nested Comments

I have a webcomic based on WordPress/Comicpress. So I wanted to use CSS to have speech bubbles on the comments. I started messing around with the CSS and got this:

https://server.ericsbinaryworld.com/notmad/2010/05/10/a-new-advertising-partner/

looks good. Yeah, I’d like to get the gravatar and name to display below the speech bubble, but that could be a question for another forum post. My problem comes with nested comments:

https://server.ericsbinaryworld.com/notmad/2008/11/12/im-a-pc/

I know one possible (and probably easy) solution is to turn off nesting. But I like the ability to reply to specific comments.

Is there something I’m missing on the CSS that would make this possible? I’m having a hard time finding a lot of CSS and Comment resources on Google post WP 2.7 (when they simplified the comment code).