You're a mod and you're telling me using a mm, especially in the case that both people are indeed the same person and they're just using it to transfer funds, isn't bypassing the system?
Look, it's simple. If someone has a static IP, they can't bypass the system at all since he would have to log in from both accounts anyway to do something. If it's dynamic, and they really wanted to, they could easily change the IP and so bypass the system. If it's dynamic and they have "trade canceled," it just means the system is not doing its job. How is flushing the IPs about 20 days old risking the game with cheating? Dynamic IP users would have their IP changed numerous times by then, and static IP users would be just as "stuck" with not being able to cheat (if they wanted to) as they were 20 days ago, thus making the system just as safe as it is now minus screwing honest people.