I was very aware, and watchful after that first chapter, of any and all smiles offered by any character. Smiles are masks, yessiree. And, yes, Lupin is definitely wearing one all the time, while Snape is too, but with different results. Great job of making me smirk during that Occlumency lesson in which Snape turns on the happy and the charm. I could absolutely see Snape practically slapping Lupin in the head for being so gullible, lol. And that last smile - heartbreaking. But he was very kind to do it. Now that's love.