About as tactful, and just about as smart. Everywhere else I have to walk on eggshells.
Speech is ever-changing. The written language is a bit more static, as it should be. Not everyone who speaks English can understand every other speaker of English. Everyone who can read English, however, is supposed to be able to understand all modern, written English. That's the standard by which I grade my papers. If it's understandable, I don't grade off much for incorrect grammar/punctuation. However, the only ones who can read Ebonics tend to be other speakers of it. Same with other, regional dialects. That does get graded down pretty harshly.