Actually... this is the result of a bug that will be fixed in patch 1.23a!

Don't worry, your favorite merchant NPCs will soon be back to saying things like "Hey, I sure love buying your random items!" and "Wow, you again? Really, I don't want anymore of the stuff filling your bag..." and who can forget "Please... I can't afford to buy items from you anymore, I have a family..." and so on.