Jonathon Owen’s Arrant Pedantry blog is always great reading for writers, editors, and other word people, but this one might be especially interesting to writers of dialogue. It discusses the difference between direct speech, when you come right out and say something (“What time is it?”), and indirect speech, when you do it indirectly (“Do you know what time it is?”). The expected answer to “Do you know what time it is?” is not “Yes” or “No” — though you can be sure that one of your wiseass friends will occasionally respond with one or the other!
Indirect speech acts are often used to be polite or to save face. In the case of asking a child or subordinate to do something when they really don’t have a choice, it’s a way of downplaying the power imbalance in the relationship. By pretending to give someone a choice, we acknowledge that we’re imposing our will on them, which can make them feel better about having to do it. So while it’s easy to get annoyed at someone for implying that you have a choice when you really don’t, this reaction deliberately misses the point of indirectness, which is to lubricate social interaction.
How one character phrases something is often as important as what he or she is saying. How other characters hear and respond to it can show a lot about those characters.
Source: “Politeness and Pragmatics,” illocution | Arrant Pedantry