Word indicating that the authority of the speaker changes the meaning

Solution 1:

This is just an example of inference, which is an essential part of communication: we always try to think of what the speaker meant, rather than the literal meaning.

This is the case even in your buddy's case: If he says "You might want to...", if you answered the literal question, you would say "Yes, I might.", and then seem puzzled when he seemed puzzled. This is basically what the android called "Data" does on Star Trek, at least at the start of his character development.

So, we always try to infer the meaning of all statements, based on the context. There's nothing special about wives here: it's just that the context of your shared communication history is very rich, and possibly complicated, and so there may be more potential inferences to choose from.