I've heard the maxim before to "know your audience." Edward Tufte tells us that this generally leads to dumbing down our message. I so get that.
Instead, he offers, we ought to focus on our message, and he quotes Gore Vidal: "Let the writer write, and let the reader read."
Edward Tufte is known for his ability to make the complex digestible. This started with a quote of his that I read from Tom Peters web site where Edward says, "To simplify, add detail." Okay, that's a head-turner of a phrase.
I found no help in interpretting that quote, and I don't find it intuitive or obvious. I do, however, feel something simmer on the backburner of my brain. I'm cooking on this notion...
I think I find some help, via the link I provide above, when Edward says that we ought to "reduce impediments to learning." Adding detail to something is a means to answer the questions that burble forth when confronting a troublesome concept. I think for most of us, when presenting complex material, we want to reduce it to bullets or charts. And that can be helpful. But if the reader truly seeks understanding, we make it easier to understand when we provide detail and background that the user can drill into, if necessary. Understanding brings the "A-ha!" sense that we hope to invoke in our audience. Then our point is obvious and we've truly communicated. This may be the simplicity of which Tufte speaks.
No one listens well when we dumb down our message. That's not knowing our audience; that's condescension. Rather, when we challenge folks to come forward and join our perspective, then our audience knows us.