If you're the receiver in a commercial transaction, the 2.4% and fixed fee is taken from the payment total and the sender doesn't incur any direct charges from PayPal, so I guess they mean if your buyer uses an international card it will cost the seller an extra 1% ?:| (For a personal transaction, the sender can choose who pays the fees, but in a commercial transaction it's always taken from the receiver's total).

What is the definition of an "international debit or credit card"?

If indeed the seller has to pay a 1% fee too when a buyer uses an international card, I wonder if it just evens out. E.g. the buyer pays the 1% extra (if it does to the seller) and the seller pays the 1% extra fee back to PayPal... who knows. Maybe both fees just go to PP.