It is hardly worth bothering how readable is "local code". Following the same patterns across large parts of the codebase is what makes the codebase as a whole

It is hardly worth bothering how readable is "local code". Following the same patterns across large parts of the codebase is what makes the codebase as a whole readable. Those patterns may even be complex, as long as they are used over and over without too much deviation and flag-explosion the codebase will be readable. In short local isolated code can be as bad to read as it wants, as long as it doesn't infect the codebase as a whole (like through the use of shared mutable state or through a bad API).