As far as whatever “prohibited conduct” was done, this was the first and only item I’ve ever sold on here. Here are the messages with the buyer. Clearly there is some issue here that Mercari refuses to enlighten me with.
I reached out to @mercari_app support and all they had to say was that I sold a “prohibited” item. They refuse to send me my MacBook back and have already refunded the buyer without my consent. Furthermore, they keep avoiding any support and refuse to return my property.