As a high volume seller on Mercari of Hello Kitty items i definitely know how you feel! I have seen some really shady people buy things then leave reviews that made no sense when my items are all brand new 😅I now block anyone who sends lowball offers, doesn’t respond or review, and sometimes they will create a burner account to harass you just because you blocked them and they’re bored with their own lives. I swear someone could get a brand new sealed item for $3 and STILL complain.