I am locking this thread, as there appears to be a bunch of contradictory claims going around.
At the end of the day, the premise is simple - don't trade for promises. If it cannot be put in a trade window at a Dojo, then you should not be trading it. If something were to go wrong with your trade, such as being scammed, a disagreement down the line, or something was done in bad faith, you lose the ability to go to support to have it fixed. If someone is offering you a large amount, you also run the risk of having that platinum reversed and a deficit being placed on your account, leading to other issues that you are going to have a hard time fighting.
Best way to avoid all that headache? Just don't do it.