Speak
The Speak page houses an experimental threaded discussion board. Hopefully it's pretty intuitive: you click a post's "X Replies" link to see its replies or post your own.
Being an experiment, I wouldn't be at all surprised if I eventually deem the Speak page a failure and scrap it completely, so try it out now, while you have the chance.
Privacy: You can provide a Name, Email and URL with your posts, but you don't have to provide anything. If you provide your email address, it'll only be visible to Adam (the artist) and Alec (the webservant).
Old posts: You can't reply to a post that's over two weeks old, and you can't post anything new under an old month.
Bookmarking: To bookmark or link to a particular post and its replies, right-click its "Replies" link and choose "Bookmark This Link..." or "Add to Favorites..." or however your browser phrases it.
Javascript: You need javascript turned on to post.