Superhost, as it says in the name, is a status awarded to a HOST, not a listing. Therefore, it is not possible for it to be simply transfered to a new host. They must earn it, like you did. And reviews are as much about the host as they are about the listing itself, so those also can't and shouldn't be just transfered to a new host. Who's to say they'll keep it as clean as you did or in as good condition and with all the same furnishings? Additionally, you can't just hand over hosting responsibilities to someone else and walk away from reservations that were booked while you had the listing. Just as you wouldn't/shouldn't be ok with a different guest showing up than the one who booked, guests wouldn't/shouldn't be ok showing up to a different host than the one they had originally booked with. These are Airbnb rules as outlined in their terms and conditions.