Just remember to be respectful. If the buyer or seller is the first one to leave an unprofessional reply (feedback) don't try to "get back at them". Instead, try and resolve the conflict the best you can! If the problem escalades, contact Ebay and PayPal to help resolve these problems. Try to avoid giving and receiving negative feedbacks the best you can. Sometimes people are just having a bad day and you might be the scapegoat of their anger. Feedbacks can always be exchanged and replaced!