Yeah as discussed there are a lot of different reasons you might want to talk to an NPC, and the underlying reasons (being of a different nature) are all handled through different systems, some of which the '?' system is currently unable to detect. So with a complete list I could go in and see if there is some way to rectify it (there might not be without a whole bunch of special code, I'm not sure yet).
Thanks for the list, let me know if there are more.