People misusing the star system is a problem, but the real problem is that we are forced to care when people misuse it.
(To correct this specific problem, I would recommend low-tolerance hellbanning. If a positive review is accompanied by a one-star rating, that user's ratings and comments will never be seen by another user again.)
However, I saw a small burst of bad reviews on an app I used to work on a few months back - all of those reviews including the developer replies are now 'missing'.
Its possible they merely flagged the reviews and Google got rid of them because they were rude. Possibly the OPs removed them because the developer got in contact to ease their pain somehow...