Typography is for the benefit of the reader, not the writer.
This is obvious if you’re a designer who didn’t write the text you’re working with. Then you approach the project as a special kind of reader—one whose job it is to create the visual component of the text so it reinforces the meaning.
It’s a more difficult principle if you’re a writer who has to handle your own typography. Then you have to negotiate the conflict between your primary perspective as a writer and a simulated perspective as a reader.
“But every writer is also a reader—I end up reading the text several times while I’m rewriting it.” In a mechanical sense, yes, you’re reading the text. But you’re reading it only so you can rewrite it. You’re not reading it for the same reasons as your reader—to learn and possibly to be persuaded.
Always be asking yourself: what does my reader want? Because your reader is quite different from you:
|Interest in topic||High||Low|
|Persuadable by other opinions||No||Yes|
|Cares about your happiness||Yes||No|
Unfortunately, professional writers sometimes imagine that the comparison looks like this:
|Attention span||Long||Whatever it takes|
|Interest in topic||High||Boundless|
|Persuadable by other opinions||No||Barely|
|Cares about your happiness||Yes||Of course|
The only reader who might match that description is your mother.
Typography has to be oriented to your actual readers, not idealized ones. Writers often get attached to idealized readers because those readers are easier to please. Don’t be lazy. Work hard to see your text as an actual reader will. You won’t get it perfectly right. But a rough approximation is better than no approximation at all.