> Are there real-life cases where DISTINCT is the best choice by whatever metric you prioritize at the time

Indeed, along that line, I would say that DISTINCT can be used to convey intent... and doing that in code is important.

- I want to know the zipcodes we have customers in - DISTINCT

- I want to know how many customers we have in each zipcode - aggregates

Can you do the first with the second? Sure.. but the first makes it clear what your goal is.

Partly in jest, but maybe we need a NON-DISTINCT signaller to convey the inverse and return duplicate values only.

SOMEWHAT-DISTINCT with a fuzzy threshold would also be useful.