Why your blog comments have less of an audience than new blog entries
Expanding on a remark in the previous entry: I think there are several reasons why your comments are likely to get less of an audience than new entries. First, in most blog setups new comments are less obvious to readers than new entries, as your readers have to go back by hand to look for them. This is especially so if people are only interested in a few comments.
It's possible to work around this with a different blog layout, but it does mean a moderately radical change from how people think of blog front pages and so on. I suspect that it would work better for a blog that already mingles quick links with regular articles, and I think you would want to promote only some of your comments this way, because many quick comment replies require too much context.
Second, I think that many comments are intrinsically less interesting than a new entry, because they are effectively expanding on some aspect of your original entry. They are thus for people who are so interested in the topic that they want even more, and not as interesting to people who were satisfied with your original entry in the first place. This isn't always the case, but to the extent that your comment replies are of general interest, you might as well make them full entries.
(And some comment replies are only going to be interesting to people who read the comment that you're replying to, since they're just correcting or reacting to those comments instead of expanding on your original entry.)