We cannot discern a forced user shutdown from a power loss. Right now to safely savescum you need to save on each stairs, copy the file, reload, etc. It's tedious, as it should be. If we made an autosave at each level start, that would make savescumming trivially easy, and also ON DEMAND (in contrast to needing to prepare).
Most people that savescum, do so, because they've yet to discover the huge potential for thrill and excitement that permadeath offers. By providing them with a trivial way to do so, we forfeit the chance of them actually playing the game as intended.
There is a solution - we could autosave on each move - however, DoomRL's internal design choices make it VERY hard to implement saving on the spot ( I could give you a long technical explanation but it's late and I'm tired, just trust me that the amount of time to implement that would be much better spent elsewhere ). That still would allow on-demand savescumming, but not after getting into a deadly situation. I quite possibly might implement that for Jupiter Hell though.
BTW, the mortem.txt may be just a text file, but there's a small checksum embedded in the score value, so I can actually spot blatant edits :P.