[sfn42]

I personally don't actually see it as a project management issue so much as a developer issue. Maybe I'm lucky but in the projects I've worked, a project manager generally doesn't get involved in how I do my job. Maybe a tech lead or something lays down some ground rules like test requirements etc but at the end of the day it's a team effort, we review each other's code and help each other maintain a high quality.

I think you'd be hard pressed to find a team that lacks this kind of cooperation and maintains consistently high quality, regardless of what some nontechnical project manager says or does.

It's also an individual effort to build the knowledge and skill required to produce quality code, especially when nobody else takes responsibility of the architectural structure of a codebase, as is often the case in my experience.

I think that in order to keep a codebase clean you have to have a person who takes ownership of the code as a whole, has plans for how it should evolve etc. API surfaces as well as lower level implementation details. You either have a head chef or you have too many cooks, there's not a lot of middle ground in my opinion.