I agree with the sentiment that there should NOT be a flag on gold bar fleets. That is too risky and is not a good balance for the game. I say this as someone who plays the game as an opportunist and could benefit from the flag of gold bar shipments in the short run. In the long run, there would be little gold bar movement, which I see as very negative for the game.
In the time that I have been playing the game, I have seen a wax and wane of profit by hitting lit fleets and of casting voodoo to go after high value targets. The best profit for me was when traders were making and carrying a lot of gold coins. Then, my attacks could get me more gold. I see the flags for gold bar fleets only leading to fewer people transporting and profiting from gold bar fleets, which leads to lower profit for traders, which leads to lower profit for pirates.
Slindur