GSS -- would you accept that, although Jim's quote from Walter Pardon focuses on his recognition of tune modes, it is also possible that any singer with a considerable repertoire would also have a fair instinct for what we might call 'traditional' texts?

I know a fair number of current Scottish singers, steeped in traditional song for decades, who would approach a song from the point of view of communication with an audience: this would mean that they might adjust word order and adapt the tune so that key words would sit more comfortably on significant melody notes etc. The expectation was that the end result would fit seamlessly with the main body of the original text. I can't believe that this is any different from the great singers of the past (Walter Pardon, Jeannie Robertson, Corny McDaid et al) who would all have had opinions and preferences on the "right way" to lead out a song.

As to the notion that traditional singers would confuse written songs with traditional repertoire (thinking of material like 'Shoals of Herring', 'Yellow on the Broom' etc.), surely that's more a matter for congratulation than concern?

And finally, I myself have 'constructed' a tune -- entirely on the white notes of the piano (whatever mode that might be) -- for the ballad Lady Diamond when I wanted to use it for a workshop situation, where participants would have no prior awareness of the text and would therefore be approaching it from the point of view of communicating the story (rather than imitating a previously known performance). In that particular instance, it seemed appropriate that the melody should attempt to sound as old as the text.

So, IMO, the most important thing is that the songs -- especially the old songs -- are sung, and sung in a way that links to an audience.
I'd have to say that my own personal preference is for unaccompanied song because, when well done, it communicates to me on a visceral level that accompanied song seldom matches. (But I do make an exception for certain instrumental music that reaches parts of me that song doesn't -- and I'm talking about my feet!)