Anyone with the [close votes privilege][1] can make up their own close reason by selecting "Other (add a comment explaining what is wrong)". The reason is also posted as a comment, and other users can then select it as the close reason, but only on that post.

This has been available for [nearly two years](https://meta.stackexchange.com/q/184154/189912) now.


  [1]: http://serverfault.com/help/privileges/close-questions