This time I thought about nursery rhymes. If you know your history, you know that they have hidden meanings. “Ring around the rosie” was a story about disease; “Hey Diddle Diddle” was a character contrast within a famous household.
–What if a bard really DIDN’T tell the true meaning of one of those rhymes?
The temptation would always be there. The easiest thing to do would be what Willem Dafoe did: write a story that uses the same information. A bard could make sure he didn’t get as close as, say, a writer, but would always tend to reuse meter, rhyme schemes, phonetic themes, plot devices, archetypes . . . well?
Obviously people today don’t mind repeatedly and radically altering old works of fiction. Something else, everyone knows the old saw about ‘winners writing the history.’ How many times can a world essentially ‘lose’ world-changing truth? For an answer to that, I can recommend the old short story “Nightfall” by Isaac Asimov.