Heya I'm from the Cait Sith server and I'm at work bored off my *** so I figured I would post. As to the whole contacting a GM I have gone through this several times myself personally. They will NOT take any action unless the physically witnessed the MPK attempt. That is how the gilsellers are able to get through the loophole. Nobody knows when they are going to get MPK'ed, the sellers know this, and they also know unless a GM happens to be randomly watching that area, they WILL get away with it. It sucks and it is complete ********* but it simply is the way it is sadly. You will get the standard we are looking into it response, because the GM's hands are tied. The only feasible way that the GM could get them is if they sent you a message before they MPK you. Then he could go back in the chatlog and see it.
As to the whole gilseller situation itself, I believe our server may be the lowest of the low when it comes to them. Get ready for this one. We actually have NA players with **** reputations, forming linkshells with all the gilsellers for all the endgame things. We now have gilsellers in all the Dynamis areas, Sky, Sea, pretty much everywhere. The NA's get the bodis they need for the endgame things, and the gilsellers take all the Dynamis currency. It's a ****** up thing and the GM's can do nothing about it unfortunately >.<