It looks like you've got your blog set so comments need to be approved by you before they're publicly visible (so to us it looks like you're replying to nothing). To approve a post, click on the "Approve" button down by the "Edit," "Quote," etc.
If you don't want your comments to need approving, click on the "Your Blog Settings" tab, and uncheck the box next to "Approve comments posted on your blog?" in the settings tab. =)
-Ziko