Google translates:
"Have experienced that more and more people book for others. You can assume that they do so because the one who comes may have a bad average value or have other intentions than what is said. The person who books has a transparent past and a good grade, but the person who finally comes and stays overnight is someone completely different. They say in connection with the booking that one is another person who comes but that the person who books represents the other. Is this even allowed? What can be done about it?"
Third party bookings are only allowed when booker uses an "airbnb for work" account and makes a booking for an employee)
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If otherwise Inform the guest third party booking are not allowed and ask them to retract the booking request.