Sometimes the guest will act "dumb". I recently received a message from the guest if I can cancel the booking, because they didn't "know" how to do it (they were under the strict cancelation). I've told them that this must be done from the guest side and if they have some difficulties regarding this, they should contact AirBnB to help them. Then they canceled (at least they tried), but I did make a full refund, because they've canceled quite early.
Maeve guest cancellations does not impact us negatively, but the hosts that cancel their bookings does.
Sure they can.. When I was accepting first bookings I was also penalised, because I wasn't aware, but now I am a superhost, so nothing to worry about.