Ok maybe it would be too intensive to run on a large forum, but...
you know when you are writing a big hefty ole comment down, and by the time you've finished it a couple of people have already beat ya to it and posted their own messages up, making your answer irrelevant... or look stupid... (happens to me a lot ha ha)
would it be possible to have a wee sidebar in the comment form, listing anyone else currently writing a comment?
I don't understand how that would help the situation you are proposing...you just know that they are writing a comment, you have no idea whether or not that comment has anything to do with what you are going to say.
I can see where 3stripe is coming from, but yeah, it would be a pretty resourcey (new word) extension i assume, and i think the idea needs a bit more thought into it to make it work. Interesting though.
I think we need a brain extension which makes us all virually omnipotent and then don't even need to communicate because we already know what everyone else is thinking.