I always assumed having to type the smile domain was more about making sure they didn't have to make both an affiliate payment and a smile payment on the same order.
Seemed like an easy way to cut off affiliates while appearing to be generous. Maybe I'm just too cynical.
Oh but they weren't forcing the customers to go to smile and strip the affiliate attribution for their session. Why, they don't even provide a link for the customer to click! The customer is choosing to actively navigate to smile themselves (when prompted by t he reminder at the top of the amazon page). So obviously that means Amazon can't be accused of doing anything nefarious to screw their affiliates (or, more seriously and litigiously, their advertising partners) out of their due credit for the sale. The customer simply chose to switch to smile. And it's all for charity so who could possibly complain?
www.amazon.com sets cookies for (*).amazon.com, though. Session cookies (and affiliate info) could therefore still be accessed on smile.amazon.com. I think affiliate attribution is just discarded regardless of cookie presence.
Seemed like an easy way to cut off affiliates while appearing to be generous. Maybe I'm just too cynical.