To opt into paying just 2% commission, simply visit the 'My Account' section of your Betfair account and select the 'Basic' rewards plan. The 2% commission rate will be applied to your account immediately and you can start making those commission savings.

For this reason alone, Betfair has no reason to ban or close your account when you should win. This is what Betfair first became famous for; peer-to-peer betting. Whilst the Exchange account won't be closed for winning, there is an additional commission rate.