dainsAndrew, please consider picking this back up. I realize your thinking was along the lines of collecting survey data, but the ability to set questions or instructions for commenters - by post - is invaluable to keeping discussions focused and deciding which comments need to be moderated.
This isn't trivial - moderation is a constant timesink with every blog in existence. Most people deal with it by not dealing with it, thereby letting unfocused or malicious commenters destroy the value of the discussion. Since the purpose of comments is to increase the value of the original content posted, this also destroys the potential value of that content.
To sum up - your idea is a great thing waiting to happen. You can show instructions right above every comment to keep things in line with your post, and instantly know when you need to moderate out problem commenters. Please reconsider supporting this (or at least the question feature) for future versions of WP?
http://wordpress.org/extend/plugins/fun-with-in-context-comments/
