I briefly worked for a company whose main product had been a FoxPro application that they rewrote piece by piece in C#, reimplementing various FoxPro idioms as they went. It was a nightmare and no one knew what any of it did. One "senior" developer tearfully argued with me during a code review that even fixing comments could have dire consequences.

I suspect that someone higher up liked it that way, because I was fired shortly after mathematically proving that something was really wrong in some of the accounting code.