I am looking at the feedback system and specifically from what I see your comments are a little confusing.
You say you want people to edit there feedback and then next say you remove that ability which is confusing to me. In our application you can not edit feedback after it is left. The admin can delete feedback etc if he is moderating things but that is the size of it. I do not beleive users should ever be allowed to change feedback just like the seller can not delete someone's feedback.
I will look at ebay to see what we can do as I would need to try and visualize things. One thing I know I will be doing is separating moderation into ad,comment and feedback moderation permissions.
Just looking at expanding things and need some clarification on your ideas.