I have noticed some coworkers have their ego gratified by being right while everyone else is wrong. Instead of simply explaining what they are doing when they are doing it, they will do something that looks wrong in a very noticeable way and wait for the backlash. The backlash gives them an opportunity to show everyone else how they were right while everyone else was wrong and also an opportunity to play victim. However, in SW development - it is not just the technical details - your behavior also matters in a big way.

In this particular case, the correct approach is to create your own library function with appropriate comments. This is why the concept of a library function was invented. It is its entire raison-d'etre. However, you are doing everything but that. Including providing justifications in hacker news comments instead of your source code.

Now inevitably, someone will change your inline code to use to_lower. This will give you an opportunity to scream bloody murder, show how other engineers don't really understand technical details, correct them and also play victim. Create a library utility with comments and link it in - End of story.