I recently heard a folk singer for the first time that has been described as 'wonderful', 'magnificent' etc

He sounded, to me, absurd. He was singing in a way that suggested he had taken on board strictures about diction - like the ones expressed in this thread - far too literally. Not BBC newsreader levels of it, just an unnatural degree.

A singing teacher would have applauded and given him top marks. I just thought he sounded like a fool.

Harry Cox did not have good diction - nothing to do with regional accents - he simply didn't. He was a great singer. He sang how he spoke, to the extent that you can.