Part of the balancing act of editing is estimating the aptitude of your audience. We can’t assume they will pick their way through a thorny patch of grammar. But we shouldn’t barrage them with bland and obvious “information” either. (Governor Jeb Bush of Florida is President Bush's brother? Really?)
This subject takes up a lot of ground. It’s something copy editors and writers spend serious time wondering about. What is obvious? What is complicated? How can I make this clear without being condescending?
Lest we forget, copy editors and writers are people too. We’re our first audiences, and our first testing grounds for these questions. If we can't understand who the personal pronouns are referring to, that's a problem. If we can't follow a transition, we should think about revising the story.
As I said: Lots of ground to cover on this topic. I'll deal with how it affects caption-writing next.