now where is the fun in that ghost?

None. I lied - I'm going to give it one last shot.... :8}

The function of feedback is not to acknowledge payment, nor thank a buyer for it. It is there for the seller (not for the buyer) to tell other eBay members about the experience the seller had with that buyer and that transaction.

If a seller does not want to tell other eBay members about their experience with that buyer until they consider the transaction (and ergo their experience) has been fully complete, that is their absolute right.

And for the record, I leave FB upon receipt of payment. I argue this point consistently because I understand and respect the decision of others to leave it whenever they like.