Originally Posted by
Gothicshark
It's a justifiably bannable offense, however, it's really hard to prove. Due to this, they only ban those accounts if they can verify that yes they purchased currency. I know that Blizzard banned a bunch of players for buying gold a few years ago, and I'm sure that SE has caught a few and banned them as well. The thing is, they might have a list of players they suspect, but until they catch them in the act, it's hard to tell. As the currency exchanges are usually done through the market with something cheap sold for maximum prices. Easy to make a list of those players, harder to tell if the buyer was actually the gold seller. which is why they limit markets to the server your character is on, and why WOW changed the AH the way they did.