Removing a coupon from an order is a full page refresh, at which point a message appears at the top stating "Coupon removed from order".

Adding a coupon is done by ajax and the old message about removing a a coupon remains, which could confuse the user as the most recent action was adding not removing.

Steps to reproduce:
Create an order and get to the checkout.
Add a coupon.
Refresh the page so the remove button appears.
Remove the coupon.
Add a new coupon.
Notice that the message at the top of the screen at this point says "Coupon removed from order"