Tunesmith--

Most people within the cultural groups we're talking about, I think, make a distinction between singing and speaking. There are different aesthetics and "rules" for each of these forms of expression. They might be quite similar or very very different.

Singing certain things precisely in one's "own (speaking) accent" is just as and no more "artificial" as doing it in another accent that is "embedded" within that song's style.

Accent is an unreliable indicator of authenticity, and correlating the expression of the "self" directly and exclusively with accent seems a bit shallow. Come out from under your provincial rock in this case, and check out what people are doing/have done musically around the world. There is so much more to it than what we might see through the narrow lenses created by the agenda-driven early English musical folklore scholars.