Illegal? I don't think so. Legality and morality are different issues.
The public knows so little of this, but it is all too clearly seen by those who will merely look..., or question how it is that central banks can flood the world with fiat money, while the prices of gold and other hard money-related assets do not rise proportionately.
Then, too, how is it that banks and commodities warehouses are allowed to lend, sell, or short trade assets that they are supposed to be holding for other as fiduciaries? Just normally accepted business practices, I guess, but it is interesting to note that every day people can't borrow money against what they don't own.
Such schemeing is what the Fed supposedly "regulates", though commodities warehouses operate outside of their purview, and are, therefore, more easily used to control markets.
AIMHO
Oh, and further to early posts, these are the kinds of messages that would be deleted as "off topic" on that other board, and the posters suspended for repeating such "violations".