…and here it gets tricky - how can you tell who bought gold? - You simply no longer can, let me explain why:
In the Real world, it is common practice to wash money that is involved with robbery and other crimes. The Villain will run a small business or company to inject money of actual crimes into the normal ecosystem. This will put the police and other authorities off the track and makes it nearly impossible to catch the source of the money flow or the receiving end.
In World of Warcraft we as players introduced our own small businesses and companies (willingly and unwillingly) to assist washing the money (gold) of such illegal activities such as botting. The MetaGoblin Video I linked in the Post doesn’t go totally into the details (as it would be a blueprint for others to replicate the process) but it shows how the gold is distributed to the gold buyer: as a GDKP Cut. GDKP is not only where PPL spent their Gold, it is at the same time an effective way for botters to inject gold into the ecosystem and put blizzard off the track.
In an ideal world this would totally work but given the circumstance GDKP is involved into this process and being the primary source where players would spend gold it is a much easier and efficient way to remove a tool of the actual gold selling chain to expose not only the gold buyer but also the bot distributing its gold. GDKP has been proven to be a great shield as giant amount of gold gets thrown left and right that you would barely notice botting gold among it.
There will always be ways and I didn’t neglect it but given the track record GDKP has in this process (it is actually involved into RMT and Gold Selling) in Era and Wrath Classic we should know better by now. The Debuff would be barely noticeable by most players as it only disables gold trades for a set amount of time. A ban of GDKP would harm fewer players than simply allowing it and ruin server economies. It would also directly hit the ppl that buy gold, as the solo gold sink that requires huge amount of gold is now gone in the game.