One problem I have with Hoid being the author of the AA is that the Mistborn ones have Atium being grouped with the other metals. I imagine Hoid would have known there was something special about it (assuming he wrote the letter in WoK) since he know’s Ati’s name. Unless he wasn’t putting everything he knew into the AA and was just recording what the people who use it know about the magic.
I finally got around to signing up. I love Brandon Sanderson’s books, like everyone else here.
Oh yeah, and I figured out the connection between Adonalsium and Hoid:
Adonalsium...Ruin and Preservation...Harmony...Melody...Music...Flute...Hoid