1) Do NOT create shill usernames and use them to create feedback for yourself or others, or you'll be banned, no questions asked.
2) Don't use the feedback area for trades that never happened. Somebody sold it out from under you and you still have your money? That's life, move on. Somebody said they'd buy something from you, but never sent money and you still have your part? That's life, move on. Exceptions will be allowed if you traveled a long way or put a lot of physical effort into accomodating the trade.