tsp – sorry, but you’re wrong on this one. That code is in use on my blog right now. When I put it in originally, it enlarged the 16×16 avatar to 32×32, but as I mentioned above, it stretched the image since the avatar was hard coded in the php/html. I convinced the fine people here at WP to increase the size of the avatars in the comments section to 32×32, so I just left that code there (since it also floated my avatars to the right, instead of being on the left).
If the OP wants a smaller avatar, that code would work (simply change the height and width).
I actually copied that code, BTW, from another WP.com blog CSS that I saw somewhere.