1. The absence of "As you know, Bob" infodump for something (an animal, a cultural practice, a superpower) common to the world, but unfamiliar to me, that I can/will eventually figure out from context enough to understand the story. Though maybe not entirely, some things just stay numinous and strange, for the reader and the protagonist.

2. This isn't really "good worldbuilding" but it just occurred to me that no one is ever nearsighted In A World Without Eyeglasses (to be lost or crushed at a convenient time). Statistically speaking, low-tech worlds should involve a lot of squinting.