Clear expository writing uses some of the same abilities and learned skills that go into a well-organized, well documented computer program. You start with a problem, develop a nicely-chunked set of arguments to address the problem, and proceed to a conclusion (or “output”). Along the way you void syntax errors, spaghetti logic, and redundancy. So I’m not sure I understand the concept of a “writing disability” in someone smart enough to code. Everyone has strong and weak areas but unless one’s programming skills are truly extraordinary, without fairly good communication skills it may be hard to climb a career ladder above a certain salary plateau.