If it's possible, (maybe there's a hack for this or the author can add this feature), I would like to see the background color for messages different in preview mode.
The reason is simple. A few times, in previewing a message a few times, making typo corrections each time, I've neglected to actually post the message. This is partly because the preview mode looks too much like the posted message.
annoying on long posts, and I've not added to a couple of discussions when a long reply was lost. I just didn't feel like recreating it.
Having a different background color in preview mode would be a nice reminder that the message hasn't been posted yet.