I usually prioritize diplomacy over everything else. You are probably better than me at this. The fact that I found an issue you didn't is probably just coincidence.

I could even be wrong. Maybe it's not an issue at all.

So I'll say "Could we move this out to a separate method? recountFooToilets seems pretty sepf contained and reusable" or just "I'd extract that method".

I don't want to say anything that implies I know better than you.

I'm pretty big on best practices, and a lot of people aren't, so when I find something like that I try to frame it as my problem, not their problem.

Especially with wheel reinvention, in-house implemented algorithms, use of low level primitives when the language provides high level things, lack of unit tests, or any other lone genius/cowboy coder/three star stuff.

I try to use the kind of tone Rust's compiler uses. "I don't have any reason to believe there's anything wrong here, but I don't know how to evaluate it, I don't have any experience with this style, it's above my skill level, and probably above some others too. Doing X is the tried and true standard, anyone can understand it, it will be easier to maintain".