Hooo boy! I performed a magnificent stunt in the garage today. I met my next door neighbor there and we chatted about my new Civic. Off he went, then I started my car and started reversing and... WHUNK!
Having been distracted by the chit chat with my neighbor, I had completely forgotten to detach the heater cable from the socket. A nasty tug. After initial swearing and poking around a little it turned out most of the damage was done to the cable itself (the pins were slightly bent), not to the car or the wall socket. Lucky me.
The damage would have been much worse, if the wall socket's locked cabinet was made of steel, not plastic. The plastic door was flexible enough to let the lock come loose without breaking anything.
Why are the sockets inside locked cabinets, you non-Scandinavians ask? Because those cables are a tad pricey, and some people have a nasty habit of stealing them. The cabinet holds the thick end of the cable behind a locked door so it can't be nicked. Also, some people may steal power from the socket.
Anyway what comes to the heater, I decided it's not worth the trouble to unmount it and move it by an inch. I can live with the glovebox lid hitting the heater. It still opens enough. And it's only a problem during the winter.