Well to sum up, bitfinex defense line is "don't double click we'll refund any loss due to us exept double click which is well known that can block the system and screw your account.". But we think it's huge bullshit, the contract is clear, the button says "close order" it doesn't so they are guilty of all loss due to the "double click" too.
So wait, their "close order" button closes your position by taking the opposite position for the same amount as your open position, not based on the open order's ID? Or how would double-clicking close order cause any trouble in any sane system?
Perhaps it's faster for them to push a new order to the trade engine without looking up order IDs?