From the website:
A comments-oriented theme, designed to make it reasonably easy to publish short, ‘commentable’ documents in a convenient, accessible, degradable way.
From a blog post about the theme from one of the original developers, Steph Gray:
You define a commentable chunk within a section (in WordPress terms, a post within a category)
Chunks within a section have ‘Next’ and ‘Previous’ buttons linking them together, plus a drop down menu at the top powered by the Drop Down Post List plugin, to make it easy to get between pages
The comment form is to the side, rather than at the bottom, and floats (in modern browsers) so it’s easily accessible at all times. Comments are listed at the bottom in the conventional way.
The footer contains RSS feeds for comments on the chunk itself, all comments and all chunk content, making it easier for readers to keep track of the discussion or even grab chunks of the document to mashup in new ways. I’d recommend the excellent Subscribe to Comments plugin so commenters can get email alerts of new comments added to the thread.
There’s a print stylesheet to make the content print in a plain, simple way; and for geek appeal, it seems to work more or less OK on an iPhone.
An online demo can be viewed here (archived copy).
The Commentariat Wordpress Theme is developed by the UK Department for Innovation, Universities and Skills (DIUS).
Update: The Commentariat Wordpress Theme tool has been discontinued. In order to access its website, view an archived copy of the site.