I have used the word sorrowful quite often in the past, sometimes in a similar situation. "My goodness, but that was a sorrowful story." (Talking with my nephew about the Quenta Silmarillion, especially the Death of Fingolfin.) I also use it when lambasting someone (like a celebrity) who is caught doing something wrong. As in: "Oh, you should have seen the sorrowful look on his face. But when you get right down to it, he was really sorry about getting caught, not for what he had done." Chances are, even though something is considered "archaic" by some, it will still show up in a dialect. There are 50 states, 13 provinces/territories, just in North America, some of whom have several sub-regional dialects. That's not even counting the 40 dialects or so of British English...
Exactly, and that's my problem - if it's a small regional thing, it should not be accepted. If it's a large regional thing, it should be. And if it's anywhere inbetween, well... that means we have to decide on a case-by-case basis, which inevitably upsets people no matter what we choose. So for cases where I'm not sure, I like to gather additional input from other natives before making changes to the course. :)
Very true, trying to make everyone happy, will make everyone angry and yourself extremely frustrated. I have a suggestion that might help. Get a good thesaurus, and an older dictionary that describes the words in detail, and some even have the etymology for words. Sadly many newer dictionary definitions just seem to lack a certain something. Compare the definitions of Education: http://webstersdictionary1828.com/Dictionary/Education and https://www.merriam-webster.com/dictionary/education . (Full disclosure: as an Historian and Theologian, I know that I have a predilection for things that are no longer in vogue.) If a word has a close enough concept, root or everyday meaning, bounce it off your colleagues. In some ways, a few extra word variants can really bring home the beauty of a language. By the way, thank you for your hard work dealing with all of our incessant nitpicking.