The very concept, the descriptions of the cloud demon (Mr Snookums, rotfl!) and Harry's wonderful interactions with it described through Snape's acerbic PoV. And the word games with the cloud were brilliant throughout and made me lauh like a loon. Writing and descriptions were just delicious throughout. I loved Snape's approach to the cure, and the bitter-sweet sad way in which Harry trying to freeze himself out of painful emotions (and, I had the impression, the company/closeness/playfulness of the cloud) made perfect sense at this very point in canon. And the Snape/Harry was just beautiful - again, the writing was absolutely superb there.
Just, um, Harry being 15 and chan are pretty much contradictions in terms...
Loved to bits and recced - one of the very few stories (so far) that rocked my socks this holiday season. Thanks, mystery writer!!!
ETA: it *was* anonymous when I read/recced it (courtesy of downloading everything when posted, so... I just had my omg, that was *you*!?! moment right now. You're brilliant, woman (and I wouldn't have guessed - it's different from everything I've seen you write so far, and has a very special crisp style that's absolutely lovely. Thumbs up!