Jesuit has coded a “Live Preview for WordPress Comments Hack” which is just very nice. I was thinking of writing something like that myself when I had a few minutes. Here is some preliminary information from his forum post.
I have ported the live preview hack from MT to WP.
Basically this hack allows your users to see a live preview of what they are writing below the comment entry box.
Currently it uses onkeyup, but you could easily change it to onblur if you don’t want the realtime updating.
Check out the hack here.
Good job Jesuit!