I don't understand this concept of flagging your account as I've never seen it. From my understanding, the game has no anti-cheat. It simply breaks if you've got the game in a certain state that the developers didn't anticipate. This includes having multiple "key" items, and having x255...
Not necessarily. Unless you're trading for more than 1000, you can technically trade any nopaew item for free. This can be done from keys to starcharts, etc.
I've once traded x100 of a tome that I didn't have and in my inventory, the tome became listed, holding a negative value. I had to earn...
Just to be clear, you use Gameguardian to perform a negative exchange, where you can receive the purchasable item for free*
* - For nopaew, you pay it for free, meaning your currency doesn't get below 0. But for burning books, your traded book can go into the negatives. This means that if you...