You dont even need to use ebay. Set up 2 paypal accounts (and yes, you are allowed more than one account, they just need to be registered to different addresses), and send money between the paypal accounts using your credit card.
It does work and you will get the points, but paypal charges 2.4% on all transactions processed and more for credit cards, so 100,000 commonwealth points will end up costing you $2400+, which isn't really worth it.