A lot of the characters spamming are hacked accounts to begin with. In game currency selling is a business, the people spamming are employee's, they're not going to give a shit if they get ganked in pvp lol. GM banning them doesn't work either because you're assuming they have the manpower to do that. If there actually were enough GM's im sure they would be muting them, suspending them or dealing with them in whatever way they see fit, but there obviously isn't enough GM's to go around. Banning people who buy gil requires an investigation, not everyone is gonna buy millions at once. They need to determine that a person actually bought gil outside of the game and didn't just make a normal trade in game, again that takes GM's time which we've already established there aren't enough GM's to go around.