John McWhorter claims some of the power of Obama's rhetoric stems from his use of Black English.
I don't live in the English speaking world to the extent that I can agree or disagree with him, but his argument resonates for what it says about language in general. The idea that the way a person uses language reflects profound aspects of identity, and that communication happens through the form of language and not only its content, while recognizing those identity codes, fits well into my experience.
This is the reason English translations of the Bible don't work, although the King James translation comes close. The others supply the content, but not the profundity of the original Hebrew.
I noticed this also when my first book was being translated into German (from English). I had researched it in German, reading mountains of Nazi documentation; then written in Hebrew, from where it was translated into English for publication. The translator from the English into the German was a good friend, and we had a fine common language. What he lacked, born in the late 1950s, was a familiarity with Nazi-German. This lack of familiarity made it very hard for him to translate my book into a German that would reflect the reality of the people it was about: German speakers of his grandparent's generation, perhaps even the language of his own parent's youth. His German was too far from it, and repeatedly I had to tell him he wasn't "getting it". Thank God, I suppose.