"What is not counted as an imperfection?
The following types of actions will not be counted as imperfections:
Cancelled orders requested by the buyer using the order-cancellation option on Amazon.com.
Pending orders cancelled by the buyer on Amazon.com.
Buyer-initiated messages that don't require a response, such as a "Thank You" note.
Buyer-initiated messages that are not related to an order. "
And in another seller help section:
"Seller Cancellations
Avoid cancelling orders unless requested to do so by buyers. Orders that are cancelled for any reason other than by buyer request will negatively affect your rating."
This would lead one to think that if a buyer writes a message asking you to cancel an order, that your metrics will remain unaffected upon cancellation. But this would require an Amazon employee to be monitoring all these emails. Unless... they have a cute little system in place that detects the word "cancel" in a buyer's message.
Still, I would suggest requesting that the buyer does the cancellation process themselves. Explain that it's really easy and ensures that they're refunded immediately (this always acts as a great motivator). Simply click on "Your Orders," find the order you want to cancel and press the "request cancellation."
<3<3
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