Even with over 25 years professional experience I still see code where logic and literal constant values (including e.g. complex regular expressions) are duplicated unnecessarily (requiring constant double maintenance etc.) as more of a problem than overly clever ways to reduce repetition that make the code harder to work with.
95% of the time developers can easily save themselves time upfront and in the future by first checking if the logic they're writing already exists in the codebase somewhere and reusing that (usually with very minor refactoring, e.g. marking a function public and moving it into a suitable shared module). Maybe 1% of the time the necessary refactoring is complex enough that it risks introducing bugs or decreasing code comprehensibility and duplicating the logic (ideally with a comment referring to the original source) is the lesser evil.
