We removed this feature because

• it is not available with all payment providers
• it is now illegal to charge additional fees for using credit cards in the EU
• it is now illegal in the USA to charge additional fees for using credit cards if you only sell online (don't have physical stores)
• it is now illegal in the USA to charge additional fees for using credit cards in Connecticut, Maine, Massachusetts, New York, and Puerto Rico
• it is now illegal in the USA to charge additional fees for using debit cards or prepaid credit cards and we have no way of identifying these when used online
• it is now illegal in the USA in many states to charge more the the actual amount of the fee incurred, which is the majority of cases is not possible to predict in advance (it often requires settlement and the actual fee is provided weeks after the transaction)
• it is restricted in the USA in California, Georgia, Indiana, Iowa, Michigan, Ohio, Oklahoma, Pennsylvania, and Texas
• policies for additional fees ('convenience fees') and the requirements to be able to charge them vary according to each credit card provider - Visa, Mastercard, Discover and often can't be uniformly applied to all sales a company makes - and it is highly discouraged by them (no surprise there!)
• our cost / benefit analysis failed to provide a meaningful ROI for the code used to manage these fees