With the Guy Fawkes reference, I meant the fireworks, not that John was like a dummy that got burned... so maybe not my best metaphor there. Maybe I should have said Guy Fawkes Night? I have kept away from spoilers for series 3, so I hope that this isn't actually one! I wouldn't want anyone to think I slipped a spoiler in there.

With the divorced parents thing, I think that John *was* trying to maintain a distance between them with the analogy. I think he wanted Sherlock to feel that John wasn't threatening him, either in taking over his role in the classroom or pushing him into something on the personal level that he didn't want or wasn't ready for.

Thank you for your thoughtful comments, always a pleasure!