@GrannysCacheFabrics : It may not be right but it is not unfair - the metric is the FIRST message of a NEW thread must be replied to (or marked as spam) within 24 hours. Subsequent messages from the same account (a buyer may have multiple accounts) are supposed to be combined into a single thread. Etsy is now putting a blue text warning / advisory on those messages they consider to be a "new message" but should semantically be called a "new thread".
Etsy has been very clear and consistent about messages / convos from the very beginning of the Star Seller program. Just to clarify so people don't think they have to respond to every message and it will be a never ending loop: the FIRST message of a NEW thread must be replied to within 24 hours. It does not matter who sent it, the subject matter, if it is a duplicate or blank or anything else. If it is SPAM then it should be marked as such. Those have always been the rules. Help Requests always start a new thread. By the way, if you are creating a custom listing based on a new thread, you still need to reply to the message.
As others have mentioned and at least for the time being, it appears that marking an unanswered message as SPAM (even after the 24 hour deadline has passed) will cause your reply percentage to change in a day or two if the original message was within the current star seller period. But be aware that doing so may cause you to miss other messages from that account.
If you have not yet done so, you might want to read https://help.etsy.com/hc/en-us/articles/4403058372503-How-to-Become-a-Star-Seller?segment=selling
