Evidence is NO WHERE NEAR enough to remove neg feedback, it shall remain 
Of course, do as you wish, when the 13 btc is paid back you can all remove it.As for this:
https://blockchain.info/tx/86e500c12af5e2123da28f489da62ab6a7409d66d44a1bc50661d532072d1e82
This payment is VERY old and no scamming happened in that round.