When yes and no get confusing: answering DO YOU MIND IF

The answer to “Do you mind if…” can be confusing for anyone, even native English speakers. Consider this situation:

A: Do you mind if I sit here?
B: No.
A: So… you don’t want me to sit here?
B: Yeah, sure, go ahead.
A: Oh. You don’t mind if I do?
B: No, I don't mind.
A: Okay. Thank you.

This confusion is from the fact that there are two opposing answers that come from two opposite ways of thinking about this question.

1. Looking at the question literally, “Do you mind if I sit here?” prompts the answer no. Meaning, "No, I don’t mind." It is the same as saying, "There is no problem with you sitting here." 
2. On the other hand, “Do you mind if I sit here?” is sometimes used more figuratively. It is the same as asking, “May I sit here?” or, "Can I sit here?" in which case, the answer would be, "Yes, it’s okay for you to sit here." These people respond with a yes to the underlying question, or the intent of the question. 

This is confusing, right? No means yes, and yes means no. Fortunately, most people will add clarification to their answer: “No, I don’t mind”; or, “Sure, go ahead." Adding information is a good communication style.

If someone wants to answer in the negative but still sound polite, they might say, "Sorry, no. This seat is taken." Or, "Actually, no. Sorry about that."

You can also rely on body language to interpret or clarify an answer—a smile and a wave toward the seat, or a frown and a wave away, can tell you everything you need to know. Facial cues and body language are said to make up 93% of communication, so use these resources fully. 

So, keep using do you mind if, but make sure you answer with a full sentence and ample body language. And, when other people answer, pay attention to how they speak. 
—
literally [adverb]—what the word actually means. For instance, the dictionary definition, compared to some casual, colloquial meaning. 
underlying question [noun]—the unspoken meaning, nuance, or context of the question.
intent of the question [noun]—the point of the question or the expected answer.