Blizzard have announced that Trading Post items are now once again refundable (in the Americas, so it’s unclear if the fix is also in for EU servers, as there has been no blue post there).
Trading Post (Source)
Update: Any items purchased from the Trading Post in the Americas are now be refundable. Items that were purchased during the non-refundable window can be refunded through the weekend to ensure affected players have the time to login and make any desired changes to their Trading Post purchases.
