I buy gold to transfer to my accounts that I'm training, I receive the gold on the mule everytime when I rwt and I have a script that automates muling gold to my accounts it takes care of worldhopping, walking to where the mule is and trading using the trade feature ingame. Mule has never been banned for rwt and neither have the accounts I send gp to, I don't think it matters that much to be honest if you're not trading HUGE amounts daily or something. Most I've done was 300m gp at once gotten via rwt then traded to accounts to use for supplies, nothing happened.