Just mentioning some facts, there nothing maplesea can do:
1) You have no concrete evidence he is selling, except this thread
which doesn't show his username or whatsoever. Even if he do, he
can deny that this thread is not made by him but someone who trying
to harm his account.
2) I think he is not that stupid to fall for your fake transaction.
If its me, I would ask him to meet at certain lan shop, demand
money first then I trade with him. So, what can you do after the
transaction? Report him when he already sold what he want? Besides
you do not have evidence.
Take video or picture as evidence and give up the transaction
halfway and ask the money back? Nah I doubt he is that stupid to
not see through your scam. There no reasons to take video or
picture during transaction.
In the end, there is no concrete evidence he is selling, maple
can't do anything, unless he is selling it in game. Thats why, this
practise had been going on for long. You can go ahead report it, I
serious doubt anything would happen.
P.S - Just for your info, I do not play maple. In fact, I hate
maple. I pointed this out is because I dislike people threatening
others.