Yes, those are good manners to have and practice but unfortunately very few pax are thinking about your laptop. Much like riding motorcycles in traffic you must take care of yourself 1st and never, ever, assume people will do what they're supposed to do.

I really do agree that it sucks and people who slam their seat back should be flogged and left behind but snce you know it is likely to happen, I suggest you take steps to help mitigate damage to your laptop.