I voted no. imo this medium is about attention. being able to express ourselves but not force anybody to see anything. while a subtoot may seem rude, it preserves this balance. responding is only likely to create strife.
EDIT: I guess I should add that I often see nice posts about someone where I think they just didn't know that person was here or bridged from the ATmosphere. do you tell them without tagging the person or assume they already know?