"I hate to say it, but repeatedly asking someone to define a folk song in a very polarising 900-post thread looks suspiciously like a booby trap...

It's all about outcomes, chaps..."

I think it's more that it can't be done. I've moved over time here from "if sounds like folk to me, it" is to more favouring (as a second time in this thread) seeing if we can adapt the 1954 type idea to reflect the way some songs or tunes become part of a wider (at least for much of the UK) scene that can not be pinned to local communites.

Opinions will differ of course. And at the end of the day, most of us find what we want (some even starting something new)..