"folk being the 'recognized creative culture of English working people' or 'labouring classes' or 'working class' ... ...Not one piece of evidence suggests that Sharp believed it"

The first chapter of "Some Conclusions" is good evidence, unless you are going to quibble and suggest he didn't think it was 'recognized'.

If someone uses word 'mediation' for a singer putting himself between a the song (or it's characters, or its authors politics, etc) and the listener then they need find another word for what Harker used it for and mentally substitute the new word most of the times they read it. If they don't they will have trouble understanding what peaple are writing about.