 Re: negative questions
Speaking personally, I would use either construction to ask a question: "Wasn't the building destroyed in the fire?" wouldn't express surprise any differently from "[You mean], the building wasn't destroyed in the fire?"
"Aren't you so-and-so" does indeed express a polite reticence, but I'm not sure I can separate that from actual uncertainty. "Excuse me, but didn't we meet at the Smith's pork roast last weekend?" is no more polite than "Hello, I hope you remember me---we met at the Smith's pork roast last weekend," but in the first case, you're not absolutely positive this is the same person.
If the person then replies, "Sorry, I'm a Jewish vegetarian, and I don't know anybody named Smith," you will be less embarrassed if you have used the first form :)
However, I am able to think of one situation where I use a negative question solely to be polite. If someone has made a mistake and you want to correct them, it's politer to phrase it as a question. "Wasn't that enacted during the first Gulf war?" is more polite than, "That was enacted during the first Gulf war," even if you know darned well that it was. (And there is always that rare case when you aren't right! so again, using this form can save face :))  |