Now here's a scenario I've not seen done: cloning. My god, it's brilliant. The way you had Harry visiting the memories, showing his quiet obsession over the years was a nice set-up for his feelings, which you then matched with Snape's in the detention memory. My favorite moment of the fic was when Snape finally addressed Harry in the 'dance' memory. It gave me shivers!
This bit made me crow in glee: "You've been given more than snogging privileges, Severus." "Witness my rejoicing," Snape said dryly. "I am."
Thanks for such an enjoyable story--I spent the better part of the evening, happily reading. Great job!