So by the time I read to the bottom of the first page, I had read the same answer about 5 different times. Crazy.
HAHA
But understandable.
Just to add my two cents in; No, there is no rule that sets how much is too much for a pirate to tax. But being an RP server, you don't know the rank of the person you're pirating, so basing tax off of rank is OORP, and then it's not necessarily true that pirates should stick to demanding cargo and guns and stuff, they need money to feed their family and buy weapons and repairs for their ships.
A pirate should be concidered lucky if he gets 5 mil in one days worth of pirating.
Now lemme plant this seed in your brains;
You say the traders using the diamonobium run is considered "power trading" and is frowned upon for technically being OORP. Right?
So, if you're a pirate and you're demanding more than 2-3mil or don't try to RP out a negotiable fee for ANY trader, that could be looked at as "power pirating" and concidered OORP. Because, well, unless you're a terrorist, you'd be looking for the quick buck and moving on to the next trader, and possibly taxing the same person more than once; Which would be more likely to happen in a real life situation, ya know?