ok here is some of my ideas on how this should work.
under the avatar there should be a line with feedback: #. Then under or to the right should be a button to leave feedback.
When you click that button it should take you to another page with options with a pull down or radio button for either leaving positive or negative whether is was a buy/sale/trade, a comment box with a limited amount of characters (maybe admin can set this char limit).
After that it should add a feedback point or subtract one depending on if it was negative or positive feedback.
You should be able to view a users feedback by clicking on thier feedback number. I think you shouldn't mess with the regular profile other than adding a line perhaps with thier feedback score. I think you should just add a new database and have it so when they click on thier feedback it goes to that persons feedback page. It will list thier feedback score, and (like ebay) list the people who left feedback and whether it was positive or negative. i think positive feedback should have green background and negative red.
A GREAT example of how i think the mod should be made can be seen one www.keyhunt.com
it's a VB board but they have a WONDERFUL custom made feedback mod which is perfect for almost any feedback mod needs.
Please contact me as soon as you read this so I can ask you a few questions about what your thinking on this project.
The main thing though is that the admin should have FULL editing capabilities. Admins themselves should have the option to change any data on a users feedback page. perhaps in the config you can have it where you type in the user name to edit feedback and it takes you to another page where you can edit anything on that oarticular users feedback including comments and such. they should also be ablke to delete feedback andwhen it is deleted the score should reflect the new feedback (sometimes people forget to add stuff like that).
Also, the admin should have the ability to set a time after registering to be able to give feedback like 24hrs after registration or something to reduce jerks making new accounts just to spam feedback. there should also be flood control on how often people can leave feedback.
I think the front end of this mod will be easy but it's adding all these editing and settings and back end stuff that will be difficult but it's really essential in a mod of this type because when your dealing with buisness transactions and money feedback plays a very important role and people shouldn't have to worry about whether a persons feedback is real or not so those options will be very important.