[Obvious ideas on writing being either for yourself or for others. Paul Graham has also written things to this effect.]
I think there’s at least two distinct ways of viewing writing which seems relevant to rationality: writing as a way to help yourself versus writing as a way to help others.
The first view is about writing for the development of your own thoughts. Here, you’re using the written word as an aid to your thinking. By explicating, you’re able to see more of the implicit connections between your thoughts. And by using an essay as a way to explore ideas, you can end the essay with something novel—perhaps a connection you hadn’t seen before sitting down to write.
The second view is about writing for others. You need a working theory of mind; rather than just working things out in your own head, you’ve got to figure out how to work things out in another person’s head. Ideas like context, examples, and inferential distance come into play here. They’re all tools meant to try and overcome problems presented by the illusion of transparency.
Related to the title, you can think of writing as the output of a process generated by your thinking process; you tried to figure something out, and the writing was a byproduct. As a result, the ideas are split between your head and the paper. (Failing to distinguish which ones are where seems like a big contributor to the illusion of transparency.) When writing for an external audience, though, you don’t have this bifurcation. Everything needs to be on the paper: it’s the only input you’re allowed.
This seems to be why rewriting essays is good. The first pass is allowed to be as poorly written as you like, as the main point is figuring out a good structure of ideas in your head. Once that’s done, you can solve the second problem of figuring out how to structure them well for an audience.
I claim no originality with this view; still, I think this is interesting to consider because it once again represents two ends of an axis you can trade off against. Writing for others tends to be costlier for the writer, as it’s less immediately connected to the direct flow of ideas.
For me, I think I’ve internalized some of the useful best practices for writing for others like the liberal use of examples. The result seems to be that most of the things on MLU end up being ideas I already have some sort of background on that allows me to write them in a way that focuses on introducing the ideas to others.
I think pivoting to things that I know less about might be fun, at least for a while.