should I say please to ChatGPT?
Say please if it feels right. Research on politeness finds the effect on quality is mixed and often tiny. What reliably changes the answer is what you actually tell it: the details, the format, the context you give.
Politeness studies on language models are genuinely mixed — a few find a small, task-dependent bump from courteous phrasing, most find no measurable difference, and none find a large one. The bigger lever, in every study, is specificity: what you actually tell the model about the task, not the tone you say it in.