I would be less likely to make false reports if the most useful information was clearly stated at the top of the page. I want to see the message itself (subject and sender), not the technical-complex headers, to remind myself why I reported it. And I want to see the age of the message. Everything else is relevant to SpamCop's calculations, but I don't think it helps any human beings. Unless you have memorized the IP blocks of known spammers. Human beings judge a message as spam because they can tell the sender or the subject is fraudulent. That's the important information that we use to decide whether to click Submit or not. Don't dilute it.
This is how I would change the display, adding more blank lines too:
SpamCop v 1.389 © SpamCop.net, Inc. 1998-2004 All Rights Reserved
Here is your TRACKING URL - it may be saved for future reference:
Skip to Reports
Message is 0 hours old
From: "Joe Blah" <jblah[at]blah.com.cn> (We sell hot stuff for an affordable price)
HotStuff, also known as SuperHotStuff
- half a pill lasts all weekend
View full message
etc. etc. Put anything else here if you want.
Send spam Report Now (but you may as well put the submit button after the message, instead of making us scroll down when we're not going to read it anyway)
Or, there could be a Spamcop for Dummies option that people like me could use, and the rest of you could continue to view all the information.