Using metaphorical straws helps prevent injuries to real camels. ,

D3 does indeed look quite useful for commenting, though I'm not seeing if there is any real collaborative editing capability as well.

The Digital Document Discourse Environment http://d3e.sourceforge.net/, has many of these capabilities, in particular the two pane method for commenting on user-specified fine to coarse grained sections of text. It also allows for comments on the comments, which is quite useful.
It's open source, so the feature set could be built-upon.

Further to the angle of revision-control and undo being tightly integrated, there's some interesting stuff happening in "e for Windows" which started partly as a way to get a TextMate-compatible editor on Windows. It's wxWidgets-based so theoretically cross-platform although the author has said he won't do a Mac version out of respect for the TextMate author.

http://e-texteditor.com/blog/2006/making-undo-usable

I don't think his user interface is actually suitable for your goals but may help with the use cases.

Another interesting, albeit old, paper is http://www.ifi.uib.no/konf/nwper98/papers/persson.ps
on combining revision control with editing.

I suspect there is a lot of similarity between the chunking of textual lines of code into classes and methods and the natural chunking into paragraphs and tables of your editing environment.

In both cases, whilst merging, splitting and reordering of chunks may take place, edits within them are usefully treated as bounded by the chunk. Hence, discussions of programming-oriented editors for OO languages become relevant ;-)

Of late, not much has happened. I've been working on a spec and use cases, but have been bogged down by other projects for a while. I hope to get back to it soon.

Wassup? Where did the project go, is it stalled, being worked on furiously in secret?

I'm too busy until some time in 2007 to do other than indulge myself with an occasional peek but there's a lot of synergy between this project and other stuff I've been working on and thinking about with regards to storing and choosing variants of bits of a rich document.

Some thoughts so far:
1) I think settling on a version-control system as a backend is a huge rathole down which the entire project will disappear. The semantics of file-oriented revision control are not what you're discussing. In particular, you want more incoherent merging, picking bits out of a set of changes.

2) I am playing with a tablet (I know, we're all still waiting for iTablet). These things are made for editing!

RE: darcs -- there are easily available pre-compiled versions for Mac OS X. Don't get bogged down in implementation details too early.

QuickTopic is quite good at collecting and displaying a group's comments on an bit of text; the only problem is that it's a bit of a pain to set up for more than occasional documents. Ideally a program like GroupEdit would build in such functionality so it would be highly fluid.

By all means, include outlining features - the sooner the better!

Check in/out management sounds like a solid first step, while the reconciliation rules get hammered out.

Columns, to see different versions of the same part of the text or to show comments or related links/references, and the ability to see 2 different parts of the same document simultaneously, are very useful tools to boost writing productivity.

It would be instructive to hear how well you (and others) think QuickTopic does this.

Regarding the color problem, how about a fixed color for each person, followed by a number to indicate which session by that person (or alternatively which "pass" -- by anyone -- through the document)?

>the showing of different text colors for different authors,
Suggest change to:
showing different text colors for different authors,

>storing different projects and archiving of completed articles
Suggest change to:
storing different projects and archiving completed articles

Excellent comments, John, thanks!