IMPORTANT NOTICE: When you submit this form, Amazon Payments will replace your email address with one provided by Amazon Payments in order to protect your identity, and forward the message on your behalf.
That statement is incorrect. The merchant sent a response to my questions directly to my email address (i checked by looking at the Received: headers, of course), not via some anonymous one provided by amazon. Also, the email they were responding to had my email address in the From: line.
No big deal, but someone should fix that.