Case 1: A local transfer of USDT
I don’t know why Subscan shows a fee in DOT, but you can see from the event log and address history that it’s never had DOT and paid the fee in USDT.
Case 2: Sending USDT to Moonbeam
It did indeed fail on Polkadot and on Kusama, I stand corrected. It really should have been handled by the TakeFirstAssetTrader and I need to look into it more. Obviously that should have some test cases. Will log an issue and make sure we fix this.
Haven’t looked into sending PINK from Moonbeam yet, but I don’t have control over the XCM programs they send. Will look into making a demo though.