Well, hellbanned.

Given a random character that was involved in a transaction, name one metric that can reliably determine the likelihood of the traded goods being malicious. One.
As far as you know, I'm not innocent and as far as I know, neither are you. As far as Nexon is concerned, no one is. And I'm not just talking about being unknowingly involved, I'm talking deliberate malicious intent.

Shutting the game down, unless it helps expedite the investigation, is a childish sentiment. "I can't get the toy so no one else may play with it." If you want the problem resolved instead of being swept under the rug, deal with one of the two outcomes: rollback or tradeblock. You'd rather have a rollback? Too bad someone else prefers tradeblock and there is no good reason why Nexon (or even I, if put in their shoes) should or would favor your or their preference over the other's. The decision may be arbitrary, but it happened. Deal with it.

Yeah that's exactly why they're investigating everything.
Not terribly efficient, especially since they missed some accounts with hacked goods with the block, but oh well.