This post contains spoilers for Mistborn Era 2. You have been warned.
Big brain idea: Szeth is no longer Shin, he has been replaced by a Kandra. Specifically, Paalm. The art for the chapters with Szeth's POV have him making a facepalm, or "the face of Paalm," so to speak. It's just crazy enough to be true. We don't really get to know any Shin other than Szeth, so there's no way to tell if this is acting, but Paalm is a commensurate actor. Szeth is also moderately unstable, as was Paalm. Furthermore, the fact that Szeth has a Nahel Bond does not disprove this theory, as per this WoB:
Lastly, there was some time between the death of Lessie (AKA Paalm) and Paalm's reappearance in Shadows of Self, I believe Paalm spent this time on Roshar disguised as Szeth. This lines up with the Cosmere timeline, as Mistborn Era 2 occurs ~9-10 years after the first Roshar quintology as per this spreadsheet made by the excellent BeskarKomrk. This probably means that Trell is somehow connected to Roshar, possibly an agent or manifestation of Odium, but I digress.
What do you think? Is Szeth sus? Am I crazy? Can we trust the POV of a character who has suffered severe mental trauma?