@TiffanyTreasureShop: For Star Seller you need to reply to the FIRST message of EVERY NEW INCOMING THREAD 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. Remember that the Star Seller metric is NOT all new messages but only the first message of all new incoming threads.
Subsequent messages from the same account (a buyer may have multiple accounts) are supposed to be combined into a single thread, but there are exceptions. For example, Help Requests always start a new thread.
Have you checked the applicable CSV file available on your Star Seller page? When you look at the file remember that that the dates / times are in UTC (not your time zone), only the first message of a new incoming thread is included (all that counts for Star Seller), and usually a new incoming thread is not included until after the 24 hour reply window has passed regardless of when you replied. There is also a link to the actual thread.
