I think the groups could make a fine comment system, of course my blog doesn't have the visitors to show how it would work but I did build such a thing.
In short I started a group for my Blogger blog and it's comments should turn into topics.
lol, I should be uploading pictures I know.
A subscription to read the replys to your replys . yahoo groups are divided under divided subjects, could give the blog some more subject? A group is perfect for that, the html is already striped, the comment is the topic.
But just mail notification of comments would be great. :-)