If the customers reply was a new message just mark it as spam and it won’t count against you.
Was the customer's thank you in the original message or a separate one? if separate, then yes, Etsy expects you to respond to each new message. If it was within the original message thread, then no, you do not have to keep responding for it to be counted.
@MelodysGiftDepot As it was a separate message, then you have two choices, reply or mark it as spam. Don't do either, you will receive a ding for it.
Etsy has no way of knowing that it is the same person whom you had already received messages from.
Just mark it as spam, your rate will go back up eventually.
If the customers reply was a new message just mark it as spam and it won’t count against you.
Or if you don't want to mark it as spam (not sure if the customer would see that and be offended) - just post a smile emoji ... hey, it works!
You need to respond to the first Convo or Mark As Spam, no matter what it says. If the customer writes back in the same convo, you do not have to have the last word, as long as you responded at least once.
If they start a new convo just to say thank you, you can mark it as spam or write back to say You are welcome. You have to respond just once to each individual convo.