Plugin to handle updates/addendums/postscripts to posts?

I’ve wondered about this before — http://wordpress.org/support/topic/plugin-for-post-updates — but thought I’d ask again if anyone’s ever seen anything like this.

Think of it like author-only comments, in a sense, that are appended to the post, with their own template tags, et cetera, so that (for instance) each update has its own timestamp, a la posts and comments. So rather than manually adding updates or addendums to the post, the author could go to the post edit page, click “Add update”, write the new information, and have it appended.

Anyone ever seen this? I’d wanted similar functionality back in my old MT days, too, but never found it. I’ve had no luck finding it for WP either.

Thanks for any thoughts.