When should you decide whether to flag a posted answer as Not an answer?

I've run into this situation a couple of times, where people give an "answer" that basically repeats the problem in the original question. (Not going to give examples here obviously, but it's happened.) So a hypothetical example might be a question like:

I've noticed that addition overflows just get wrapped around in x86. Why?

and a hypothetical non-answer might be something like:

x86 naturally wraps around addition overflows in numbers, just like MIPS and other architectures. You need to be careful when performing arithmetic; check the carry/overflow flags to see if something overflowed.

On the one hand, this doesn't answer the question. But on the other hand, it's well-written (no specific quality issues), and it seems to answer the question.

Should an answer like this be flagged? (Sometimes commenting doesn't help, since there's just no response.)

I've run into this situation a couple of times, where people give an "answer" that basically repeats the problem in the original question. (Not going to give examples here obviously, but it's happened.) So a hypothetical example might be a question like:

I've noticed that addition overflows just get wrapped around in x86. Why?

and a hypothetical non-answer might be something like:

x86 naturally wraps around addition overflows in numbers, just like MIPS and other architectures. You need to be careful when performing arithmetic; check the carry/overflow flags to see if something overflowed.

On the one hand, this doesn't answer the question. But on the other hand, it's well-written (no specific quality issues), and it seems to answer the question.

Should an answer like this be flagged? (Sometimes commenting doesn't help, since there's just no response.)