If you're an author on a Kinja blog, you can see drafts of posts on that Kinja blog, even if they're written by other people. This is how comments appear on the Friday open thread before they're posted. 😱
To do this, all you need to do is visit [domain]/private/drafts when you are logged in. You can click on drafted posts and comment, and comments will be published at the same time as the post.
All in all, it would be nice if you didn't abuse this by commenting on your fellow Kinjateers' half-formed thoughts, but it's great for posts that are completed and scheduled for a time that you won't be around for. I've used it mostly to taunt Liveschedules and wish Kinja friends a very happy birthday. On the flip side, if you're interested in keeping things truly private as you are drafting, draft on a Kinja that is private to you, or better yet, do your drafting offline.