Yes the Heralds, thank you. I only read the Way of Kings (no extra chapters or other books, so I didn't know what the swords were called). I suppose Dawnshards would be different.
The reason I suspected Hoid may be a Herald is because he seems to be immortal—read the following:
This lead me to believe that he has lived for a long time—if this was Warbreaker, I'd say that he had a ton of Breath. It appeared to me that the Heralds were, in a way, immortal.
And also, he (being Hoid) truly is a Worldsinger, as he seems to have traveled from world to world (read the quote from Observer.) I didn't notice it until now, but Hoid is also a character from the book Warbreaker—if not a character with a different personality.
Edit: I have read the coppermind thing. Now this all makes more sense. (also I don't really care about spoilers)