The Feed Thread draft has been updated. http://www.ietf.org/internet-drafts/draft-snell-atompub-feed-thread-07.txt
Among various editorial changes, the in-reply-to id attribute is now called "ref". I also added a new warning for implementors: "Implementors should note that while the Atom Syndication Format does not forbid the inclusion of namespaced extension attributes on the Atom link element, neither does is explicitly allow for such extensions. The result of this is that the thr:count and thr:when attributes fall outside of the guidelines for Atom extensions as defined in Section 6 of [RFC4287] and may not be supported by all Atom implementations." There are a couple of typos, most significantly is a ? mark in the definition of the ref attribute on in-reply-to. It's not optional. I am an absolutely terrible proofreader so I'd really appreciate it if someone could do a quick scan over the current doc to find the typos that I know must be scattered throughout. - James