All of this is pointless anyways. They can still make new accounts and get off a few spam messages. As a stop-gap, the spam report thing is probably the only thing worthwhile. Make sure it’s account wide, too. Maybe put weights on it based on level, so that angry sellers/children can’t use a load of bots to shut people down.
More importantly though, they’ll still exist. As long as its economical for them, they’ll exist. I cannot fathom why the price limit was placed on token sales, for example, even though I could see the value exceeding that quickly. Why? The more people that can buy tokens with silver, the more you’ll have people buying them from the company and supplying them!
Hell, the cash shop items in general should be tradeable. Who would go buy silver from a third party untrustworthy site when they can just buy prem stuff straight from IMC and turn it into profit? Not to forget, if the profit is good enough, eventually it simply becomes too expensive to sell silver like that - prices in the spam have plummeted to 1/10th their original price, but are still significantly more expensive than a player could make selling prem.
On top of that, when the game goes free to play, there’s going to be a massive influx of people with no intent and/or no ability to pay for premium stuff. If everything was tradeable, then those people would still be contributing to RM sales, since they’d create a demand for it.
Throw the sellers under the bus by creating your own economy, while improving the game for everyone else also.