I disagree with tweaking the renown
Sinking a neutral is a war crime
Many of the neutrals sunk were carrying women and children
Mistakes do happen in times of war...but sometimes just a little more attention to detail by the sub might have avoided such senseless waste of life...it's not as if the neutral was attacking the sub and a rushed/pressurised decision was called for
Heavy loss of renown in-game is the least one should expect