OK, their rules in Europe seem to be different. However, here's how I have handled overbookings - contact the guest directly with their phone number, explain to guest, book guest at another property, NEVER tell booking this happened and just pay the commission. My mistake, my problem. (I have had other innkeepers demand WE pay the commission so they are out nothing on their mistake, but that's another issue.)
If there is also a FINE on top of paying the commission, no way.
We don't let booking have access to our checking account. (Thank you Copperhead for telling me this up front!)
Reply to review - that is controlled by the guest. If the guest does not want a reply, you don't get to make one.
We had 2 cards fail this week. First time in 2 years. The process to get the card updated was fairly simply - click 'Credit Card Declined' and send an email to the guest. I had email replies and info from the guests within 12 hours. (I didn't read where we have to hold the rez for 36 hours, but it's possible.) I state pretty firmly in the email we need to have a valid cc to proceed.