[My question](https://math.stackexchange.com/questions/183522/unramification-of-a-prime-ideal-in-an-order-of-a-finite-galois-extension-of-an-a) was recently voted to be closed.
One member said it was because the question is extremely specialised.
I don't think it is extremely specialised.
It's a criterion of a prime being unramified in a Galois extension of an algebraic number field.
But even if it was, I have no idea why it should be closed.

So my question is:Is voting to close okay if one thinks it's extremely specialised?

I'd like to point out two problems related to this.

(1) One usually never knows that a question is of interest for only a small number of people.

(2) What is the harm of letting it be open?