I am going to suggest a system that borrows from League of Legends Tribunal. Here is how it would work, when a character is black listed multiple times in a short time frame, say, 10 times in 10 minutes, then that entire account would be squelched, and the characters last 10 minutes of chat would be logged. Now, on the Lodestone, that chat log (with names edited of course) would be posted and players could vote as to if the person in question deserves punishment or not. Depending on the result in say, a 24 hour time period, one of a few actions would be taken.
<10% punish : Instant unsquelch, no GM involvment.
<40% punish: Unsquelch with GM investigation followup.
<70% punish: GM review, remaining squeched.
>90% punish: Temp ban with GM investigation followup.
To be fair and prevent abuse, if you are one of the 10 blacklisters, you can not vote on your own case. And to motivate players, SE could offer a nominal amount, say 50 or so, of GC seals for each "correct" vote.


This would solve the problem in two fronts. First of all, this would allow the players to effectivly limit RMT spam with little potential for abuse. Secondly, it would force RMT advertizers to throttle their adverts on each individual account or risk making that account useless in a very short amount of time. This combined with the existing ban schedule of mule/farmer accounts would possible make the cost of doing buisness too high for the RMT companies to use this game as a valid source of income.