Nothing to add here on the technicalities, I’m just really glad to see people still talking about this. I messed around with some ideas a few years ago, but I had absolutely no clue what I was doing, a fact immortalized on this very forum. I tried to learn more and continue with it, but found myself quickly exhausted by the apparent complexity of the task and obscurity of some of the needed information. Since I gave up, I’ve noted a few people continuing to work on additional pronoun support, and to all of those people I’m very grateful. The lack of this feature has been a pretty significant barrier to the stories I want to tell when writing in Inform 6 and 7, and the amount of extra effort required to do something linguistically trivial has been both distracting and a little discouraging. “I want to get on with writing the actual characters! Why is pronoun control not a feature of the parser!” And other such complaints.
So my sincere thanks to everyone working on this. Your work is important and appreciated. 