Most version control systems have a function to keep track of who did what. Use it to find the idiot and educate it in the error of its ways. If repeated education fails, terminate the idiot or promote it to a non-coding position, depending on corporate culture.

What is "initial design documentation"? I have heard of it but have never seen it in the wild.

Within reason of course. It is hard for the code to be much simpler than the problem it solves or the algorithm it implements. Some code will require a bit of study to understand, no matter how cleanly you write it. Sometimes it makes sense to use a less optimal algorithm to simplify the code but sometimes you actually need the performance.

So what you are saying is that IT departments would prefer not to exist?

Couldn't the code be written in a way that gcc can compile efficiently then? Seems like a simpler solution. For a large static switch a perfect hash might be an option.