I don't think anything I've written has been described as 'poignant' before, so I'm just, guh, so flattered right now - Thank you! <3
And then there's the underlying threat of Sirius. He's always there in the background. He's always a part of the equation Yeah, for me, Snape/Lupin doesn't really work without Sirius hovering about in some way. I think, whether Snape likes it or not, it's always going to be threesome, of sorts.
And I shall try not to write my own 'Author's Notes' ever ever ever again :P