Definition of Folk Music ,decided by the International Folk Music Council in 1954.
Folk music is the product of a musical tradition that has been evolved through the process of oral transmission. The factors that shape the tradition are: (i) continuity which links the present with the past; (ii) variation which springs from the creative impulse of the individual or the group; and (iii) selection by the community, which determines the form or forms in which the music survives.

I'm a bit wary of getting caught in the crossfire here and Mudcat is littered with uncountable (and often unprofitable) threads and comments on this topic. But the 1954 definition is succinct and relatively objective (groan!) so a couple of swift bits addressing it might be worthwhile.

The first part of the definition (in italics above) seem to excite no particular dissension in most discussions, although there are comments about media which do. Leaving them aside;

The term can be applied to music that has been evolved from rudimentary beginnings by a community uninfluenced by popular and art music and it can likewise be applied to music which has originated with an individual composer and has subsequently been absorbed into the unwritten living tradition of a community.

Notions of "rudimentary" that might have been acceptable in 1954 are unlikely to be so regarded now that most cultures have demonstrated that none of them is correctly describable as "rudimentary" or primitive. Nobody can securely describe "beginnings" where authorship is unknown and no author is likely to accept description of them as "rudimentary". Given the progression of literacy in most communities (especially those communicating in various forms of English) I suspect it would be increasingly difficult to find examples of living traditions that remain unwritten. They might be more frequent in communities with less reliance on English in its various forms but anthropologists and ethnographers are working to minimise even these by writing them down and recording them.

The term does not cover composed popular music that has been taken over ready-made by a community and remains unchanged, for it is the re-fashioning and re-creation of the music by the community that gives it its folk character."

This para seems to be the one that most exercises Mudcatters and (to me) appear to be at the root of the 'back & forth' between our two protagonists. None of the critical terms in this para ("popular", "community", "re-fashioning", "re-creation", "folk" or "character") has an objective definition that is widely accepted even in Mudcat, let alone elsewhere. These days, its inclusion creates more heat than light and I seem to recall various stories about the 1954 conference participants that suggest it created more heat than light even then.

Deleting it is no worthy answer and I can't think of anything to modify it that is not similarly subjective; I'd reckon nobody else could either. Like almost any classification system I've ever come across in various disciplines, the form of the classification is largely determined by its function. Many of us have such widely divergent functions for putative classifications that no one system will be acceptable for most, let alone all.

C'est la vie! Vive la difference!

Cheers, Rowan