I love this fic SO MUCH. But that's not surprising, not-so-mystery author!
First, what a unique way to approach a bond fic. It was very clever to have them already in a well-established relationship. And the way you reveal that relationship bit by bit is really well done.
It felt like reading a play, where each line of dialogue has so much weight. I'm having trouble putting my finger on it, but the dialogue felt almost Pinteresque maybe? I don't know (college was a long time ago!), but something in the way Harry and Draco talk to each other, the way their words and their silences hurt each other and even when they're trying to work through how they feel there's still a failure to communicate. Their conversations were kind of heartbreaking.
Ugh, I don't know what I'm saying! What I do know is that I had to stop reading a few times, it got so intense, and that has only happened to me when I've read your work.