It does lead to an interesting thought experiment, though, with implication for the future. Let's say someone shows up today with a significantly valuable amount of bitcoin - say a few hundred - which is now unspendable because of some historical change that was made to the protocol. What does the community do, and what are the consequences of that decision?

The right thing to do would not be to deprive that user of their money, but that would require changing the protocol in some way (maybe even forking) to allow those coins to be spendable, which would be a significant undertaking for the sake of one user. Or do we simply shrug our shoulders and say "Well, sucks to be you"? What are the consequences of us essentially preventing a user from accessing money which is rightfully theirs? That makes us far too similar to a centralized bank or exchange for my liking.