Obviously the rules need some flexibility to solve special cases. I do not think anyone has suggested that you need to provide a unique hand written explanation for the 100th repeat offense. At that point just delete the spam and ban them.
BTDT. But I've also spent time thinking "uh, is this someone who warrants a polite explanation, or will that be a mistake?" It's not easy. Spammers will try to exploit anything you do, anything at all.
