I think it's very probable that Mraize is a Worldhopper. For one, I do believe that it is noted in WoR that Shallan "could not place his accent" (Words of Radiance, Chapter 43 -- "The Ghostbloods" pg. 491, hardcover). Brandon, when in native Rosharan POVs, often describes Worldhoppers in this way. In WoK, in the first interlude in a Purelaker named Ishikk's POV, notes that one of the men with whom he was meeting (confirmed to be Captain Demoux from Mistborn: The Final Empire) sort of looked Alethi, but his accent most certainly did not match his physical appearance (The Way of Kings, Chapter I-1 -- "Ishikk" pg. 200, paperback). Also, Mraize is marked in a sort of parallel to Hoid, the most famous of Worldhoppers, at least twice in WoR. Shallan received a strange visitor during a Middlefest celebration when she was about 13 or 14 years old that revealed her Lightweaving powers to her (Words of Radiance, Chapter 45 -- "Middlefest" pgs. 527-529, hardcover). Later in the novel, Shallan identifies Hoid as this visitor (Words of Radiance, Chapter 55 -- "The Rules of the Game" pg. 641, hardcover). However, when she first meets Mraize, "He reminded her of someone, a man from her childhood. The messenger with the smiling eyes, the enigma who knew so much" (Words of Radiance, Chapter 43 -- "The Ghostbloods" pg. 490, hardcover). Here we can see an evident parallel between Hoid and Mraize. And then there is the thing which this entire thread is about: "'But who is the wanderer, the wild piece, the one who makes no sense? I glimpse at his implications, and the world opens to me. I shy back. Impossible. Is it?' -- From the Diagram, West Wall Psalm of Wonders: paragraph 8 (note by Adrotagia: Could this refer to Mraize?)" (Words of Radiance, epigraph to Chapter 85 -- "Swallowed by the Sky" pg. 1017, hardcover). When I first read this epigraph, before I saw the reference to Mraize, I thought it must obviously refer to Hoid as well. A "wanderer" and a "wild piece"? "One who makes no sense"? A man whose implications fill even super-mind-boggling-awesome-genius Taravangian with awe? Who else could it possibly refer to? Then I saw that Adrotagia had connected this statement with Mraize, making another stark parallel. All this considered, I think that Mraize is most certainly a Worldhopper.