Yeah, I was wondering the same question myself.
Ahem…
http://wordpress.org/search/separate+comments?forums=1
5th link there brings you to:
http://wordpress.org/support/topic/9996
(Note that the .htaccess hacks probably won’t work in WordPress 2.x. But then this is a hack!) A more recent thread on the topic (so no search result for it yet):
http://wordpress.org/support/topic/90412
There could be others, but considering the work needed to… well, make this work, I’ve not seen a lot of requests/solutions for it.
Also, you may benefit from looking over what comments plugins exist:
http://codex.wordpress.org/Plugins/Comments
I don’t know of one which accomplishes this topic’s goal, but there are a few that do some interesting things with comments.
My visitors commented on the wrong entry – can I change the comment,to reflect to the correct blog entry?
Please advise – Charl