For a society to learn a lesson, the society has to survive.
The individual ponies only know what society taught them. I can understand that Celestia might not be able to just reprogram a pony, but there's no reason society should be that hard to mold. If you just want to make sure the ponies are taught that there was a war, there are better ways to do it than fighting a war.
My Little Pony (generation 4) has 2 immortal characters, who get a lot of sympathy from the bronies. "How sad! Poor Celestia and Luna must see everyone they know grow old and die. How much better to die yourself!"
I tried to write a fanfic saying that death was bad. But I had to make it a story, and it ended up having other themes. I don't know whether I like it or not, but it was very popular (now approaching 7000 views in 3 days on fimfiction).
I was pretty sure the message "death is bad" was still in there, because Celestia says things like "Death is bad" and "I'm afraid of dying." So imagine my surprise when comment after comment said, "Yes, immortality is such a curse!"
Why did so many people come away saying that? Tell me what you think. It will help to know that Twilight regularly writes "friendship report" letters to Celestia describing what she has learned about friendship, and that Twilight and Celestia have an especially close relationship.
Please leave comments on the google doc or here on LessWrong, not on fimfiction or Equestria Daily. Please don't down-vote the story if you aren't familiar with the characters or aren't calibrated to fimfiction voting.
Mortality Report on google docs (comment-enabled), 4000 words.
Spoilers after the bar.
I can see two things that happened: