I hear you on the point of hierarchical context, and I agree that from the viewpoint of usability and flexibility, especially in the long term and for complex algorithms it's essential to have hierarchical contexts. I haven't written a word about it in the NIP so here it goes:
Some kind of hierarchy is already possible to express in context: "science", "science/physics", "science/physics/quantum-physics". We could make the algorithm match if the trust is a prefix of the next one. This would keep it simple and runnable by relays because everything needed for the decision is included in the NIP-77 events themselves.
Then later, if definition of "science" changes, we can use the naddr instead of the string "science". 
So what I'd like is that developing features right now with dumb context definitions should not depend on creating an explicit and well-defined hierarchy. I'd like to experiment more on the basic trust/filtering capabilities. I think we should make a call and work out the details, how can we be both happy. it's much more effective in a call.