Brandon Sanderon had a WoB where he said several people became Dawnshards in Dragonsteel Prime:
"Hoid was a Dawnshard at some point in the deep past, and the reason he (even still) cannot physically harm people, or even eat meat, is related to the changes this made to his spirit. (Consider this the same fundamental principle as savanthood.) The few of you who have read Dragonsteel know that him being a Dawnshard was also the source of his immortality in that book, though the terms were different back then. (The word Dawnshard was never mentioned, for example--though the primary story of Dragonsteel (which is no longer cannon) was about several people who unwittingly become Dawnshards.)
And a preemptive RAFO to all questions on this point. :)"
