The Principle of Least Astonishment is a design guideline that you should make your behavior match what people would expect. Don't redefine equality, behave consistently, choose sane defaults, etc.
At my company we have several code bases which were written at different times by different people in different styles (although all C#). We're working on a style guide for code, and hope to standardize old code eventually, but in the meantime people need to keep working on these code bases.
Would it be appropriate to say that PoLA requires writing code such that it matches the rest of the surrounding code base, even if it's fundamentally different than the language's normal style? If not, is there another similar idea/phrase that can be used to describe that idea? Or am I way off base, and would it be better to write the new code correctly, even if it stands out from everything else?