I've taken the editor role in a couple of recent contract jobs. While the clients were both complimentary, I think I didn't do too well for one of them, where I

I've taken the editor role in a couple of recent contract jobs. While the clients were both complimentary, I think I didn't do too well for one of them, where I came in to an existing codebase with a shortage of domain knowledge -- and this is going to be a general problem for a specialist editor, more so than with prose. I was more like a copyeditor. (For the other client I'd written the code they started with.)