I know GameFlip have implemented a “duplicate code” system which won’t allow you to list the same code twice but there are ways around this that I mention at the end of this thread.
I just think it would be useful if you could mention the code to the seller via EMAIL for reference just in case a user has listed the same code twice, e.g instead of the standard email once a seller has sold an item, write this instead (code included in the email to the SELLER):
Hello X Seller,
The key/code “GAME CODE INSERTED HERE” for “Y Digital Code” has been sent and is waiting for User Z to accept and finalize the transaction.
User Z has up to 3 days to inspect and accept “Y Digital Code”. In the meantime, please feel free to contact User Z through the app if you’d like to expedite the transaction.
This does help for reference in case a seller has accidentally sold because there are ways around selling the same code twice, e.g. to relist the SAME product you can add in front of the game code a title such as CODE = or GAME CODE: “code here”.