You can try turning on Settings - Debug. The Blog Comment webpart in my test Corporate site produced the following query:
(blog.comment.generalselect)
SELECT * FROM Blog_Comment WHERE ([CommentPostDocumentID] = @CommentPostDocumentID AND ([CommentIsSpam] = @CommentIsSpam OR [CommentIsSpam] IS NULL) AND [CommentApproved] = @CommentApproved AND ([CommentIsTrackback] = @CommentIsTrackback OR [CommentIsTrackback] IS NULL))
@CommentPostDocumentID (403)
@CommentIsSpam (False)
@CommentApproved (True)
@CommentIsTrackback (False)
I would also use Brenden's suggestion to use a repeater for greater flexibility.