Changing diction is only beneficial within specific subgroups.

Tangent: This can be played for laughs. I recall a scene in the TV show Weeds in which a black marijuana grower is asking a black friend for a favor in the latter's business-y place of work. The friend's white boss sticks his head in the room to ask for a report, and the friend's accent subtly shifts when replying to the request. After the boss leaves, the grower snerks at his friend for talking white.