Seemed like a good idea at the time?" he said weakly, attempting to smile.
"It has never seemed like a good idea," said Snape.
It is amazing what one simple change in tense can do to an entire story. Whilst I was enjoying greatly the part that had come before, the almost locked in a room sensation that the two of the had going, it is this line that just makes the entire thing vibrate like a plucked harp, resonating up the spine and through the fingers. Reading in Harry's point of view, we have been privy to his somewhat shrill protestations (this is not a criticism, despite myself, I really liked him in this story) and attempts to reform .. and then this one sentence cuts right through to the quick of them both. Through all the bluster and silence, this admission just lies there and lets them be themselves, pretensions stripped away. The rest is really just icing on the cake.