How did Kwaan know to write in metal?
"I write these words in steel, for anything not set in metal cannot be trusted."
This is how Kwaan begins his inscription in Well of Ascension. But we don't know how Kwaan came to realize that it is safe to write in metal.
Kwaan figured out that something is changing the written history: "The alterations are slight. Clever, even. A word here, a slight twist there. But the words on the pages are different from the ones in my memory. The other Worldbringers scoff at me, for they have their metalminds to prove to them that the books and prophecies have not changed."
From the changes he derived that this something want Alendi to set free the power at the Well of Ascension instead of the original, more vague task of the Hero of Ages to do something at the Well of Ascension. And then Kwaan jumps to the conclusion that this something is trapped in the Well of Ascenion
But after the initial "anything not set in metal cannot be trusted", he never again mentions how he knows this. Kwaan has no knowledge that Shards see metal as glowing objects and therefore can't read whats written on metal. Kwaan only knows that metalminds aren't safe and that written words in books aren't safe.
So why would he be throughly convinced of the fact that combining these methods by using written words on metal would be safe from changes?
