Just noticed Amazon's technically non-compliant too.

I'm buying my brother's birthday present, which is a very boring gift card.

I have a HK-issued USD card saved with Amazon, but this year Amazon asked me what currency's the card is denominated in. Suspecting this was DCC-related I selected HKD.

Amazon defaulted to show the payment in HKD, at HK$8.05. Since we have a peg in place the real rate is readily ascertainable (7.76 for wholesale and 7.91 for credit cards after foreign currency conversion fee has been factored in), so the Amazon rate is over 3.7% the wholesale rate and 1.8% over the credit card rate.

It does provide clear disclosure HKD will be charged, however the technical non-compliance I argue happened is that the default selection is HKD instead of being USD or unselected. Someone in a hurry will click through the HKD payment.