When hiring, I always pay close attention to a person's writing skills. I find it to be a useful heuristic for general software engineering competency. But I actually look at this from the opposite direction - someone who's good at writing is usually also good at reading, and being a good reader is extremely helpful in our field. (Good) engineers spend so much time reading: technical books, documentation, requirements, specs, email, and of course code. Engineers who don't mind reading and are able to read attentively tend to be a lot more effective, as they will be more knowledgeable and less likely to miss important details.