The best "protection" I've seen in this space is to log all changes to the edited document, through a simple (and therefore easy to prove correct) code path. The only editor I've ever seen do this was a Xilinx schematic editor. The editor crashed all the time, but I never lost work, since on restart, the editor simply replayed what it had in its log. (This was fun to watch!) Of course this method isn't foolproof, but it went a long way making me feel confident my work wouldn't be lost.