It has been commented on other threads here that accompaniment ALWAYS detracts from the song to some degree, so is justified only if it adds more than it takes away. I subscribe to the view that an accompaniment that causes ANY words to become hard to hear has gone too far. An alternative viewpoint is to be concerned only with the overall sound, but in that case "tra-la-la" or no vocals at all would seem to do just as well.

A lot of us find drawing-room-style settings of folk songs pretty cringe-worthy, but at least the words remain clearly articulated (arguably to excess).

Opinions as to what should qualify to be called "folk song" and what shouldn't, even among the contributors to this thread (never mind the rest of anglophone humanity) seem to be irreconcilable. Words and melody as collected by collector X from singer Y in 190Z, but performed with an umpteen-piece band complete with drum kit, is one interesting test case. The opposite, words written last week about some recent event but sung unaccompanied to a traditional tune, is another. And then there are the songs that Bert Lloyd introduced to the repertoire, where much uncertainty remains as to how much he found somewhere and how much he concocted himself.

Even the corpus of collected songs that I think we would all agree are folk songs is by no means all of a piece, made in the same style by the same sort of people. There are major differences between (to give a few examples) Young Hunting, No John, Dame Durden, hunting songs, highwaymen's supposed last words, and broken tokens.