I don't know if anyone made this suggestion before hand.
This is how it works, when ever someone attacks someone with a positive fame, he will lose fame, if he continues to attack his fame will continue to drop till his fame becomes negative (highlighted in red). When someone attacks someone with negative fame he will earn fame, When someone have higher fame then the person(both positive), the person with higher fame (must be x2 the amount of fame the target have) will not lose fame but will gain fame from the person he attacks. (NPC fleet fame will still give the same).
This will allow new player to know if the target is a pirate or just a normal guy*cough cough*/trader. This will also make fame have a bit more importance then just being a number.
Usually pirates will have negative fame.