"Quality code" is one of those phrases everyone agrees on and nobody defines the same way. It's tempting to reduce it to clean formatting or clever one-liners, but the factors that actually move the needle operate at a much higher level: the people, the design, the process, and the feedback loops around the code.
Below is my personal ranking of the factors that impact code quality, ordered from greatest to lowest impact. The ordering is deliberate — fixing a poor team or a broken architecture will do far more for quality than tightening up naming conventions ever could.