Comment by mavroprovato

> I do that - seems obvious to me, but I'm also a cyclist.

You don't have to be a cyclist. Another car may be coming and rip your door off. I think that using the mirror should be obvious to any driver

> That said, when I'm in the back seat, I'm not sure if I do anything to avoid dooring.

You could turn your head 180 degrees and look behind you I guess