I put this here because it's closest to the title of this section.
This phrase has always gotten good results for me, when I remember to use it. When someone says something that I percieve as a subtle insult, or a backhanded compliment, looking at them like I'm confused and saying "What do you mean by that?" either illicits sputters because they've been put on the spot to elaborate the fact that they've said something nasty, or they rearrange it, it they're quick enough, to mean something nice or unoffensive. And occasionally, it clarifies that I've taken something the wrong way, and they really were trying to be nice.
The downside to it is that a few times I've said it to someone who really thinks they are 'helping' by saying something I find offensive, and this phrase gives them an opening to 'preach' on the greatness of their advice or opinion. So you do have to be careful sometimes. If someone isn't alert enough to realize they've said an offensive thing, you might find yourself listening to a lecture.
Anyone else used it? What results did you get?