4. Your discussion of the grammatical correctness of singular they, and the links included, is nice but it’s for a completely different usage of singular they. You and they were writing about generic singular they, whereas with non-binary people we are talking about the use of singular they for a named individual. “Everyone clapped their hands” vs. “Alex clapped their hands”. Using they for a named individual is indeed new, but it’s a very slight shift in usage, so slight that many people don’t notice it until you draw their attention to it. We need to be arguing for this new usage, that language shifts all the time and here are some other examples of it shifting, and mentioning that it’s close to historic use of generic singular they as a side issue.