Is Variety Good or Bad?

Here’s part of an article in Ars Technica that brings up a point about writing style. I’ll make the words I want you to think about bold:

Our brains are apparently really good at divvying up heavy mental loads. In the decades since scientists started taking snapshots of our noggins in action, they’ve spotted dozens of distinct brain regions in charge of specific tasks, such as reading and speech. Yet despite documenting this delegation, scientists still aren’t sure exactly how slices of our noodle get earmarked for specific functions.

Three words for the same thing. Is this good or bad? That depends, and herein lies the point of this post.

• If you’re engaged in informal writing, especially writing meant to entertain, variety is good. In fact, it’s considered gauche to repeat a word. We look on repetition as due to lack of imagination or vocabulary, and it’s boring.
• But if you’re explaining something, use the same word for the same thing every time. The reader of technical material wants to know exactly what’s going on, and giving something more than one name obfuscates the meaning. Call it “the half-inch wrench” every time. Don’t sometimes call it “the spanner,” and see the next bullet:
• Beware of using pronouns. Pronouns are supposed to refer to the closest preceding noun, and it’s easy to accidentally refer to a word that’s farther away. For example, someone might write “Use the half-inch wrench to tighten the cap screw assembly, then put it down.” Put what down? The wrench or the assembly? Be explicit.