Closing questions is important in order to get them clear and on topic before any answers arrive addressing the wrong question. Giving a clear statement of why will not only help the question poster to improve their question, but also help show others why the question needs to be closed, so they can close vote quickly and decisively. This allows a question to be closed quickly before answerers waste their time.
Clear explanation is good for the question poster, good for the potential answerers, and good for the process of site scope definition.
This can be in the form of a quick comment, or a comment linking to a new meta post, or linking to an old meta post if the reason has already been discussed.
For anyone who avoids leaving a comment because they don't want to be identified as the close voter, there is no reason to hide. Bear in mind two points:
- Once a question is closed the 5 close voters are listed for all to see.
- Closing questions is a good thing. It's not only helpful to defining the site scope, but helps open a discussion to make sure the question has the chance to become the best it can be.
We need close voters, they are vital to the running of the site. The other side of this is that it is helpful to welcome close votes even on your own questions. See them as positive, and ask for clarification of what you need to improve. Open a meta discussion for any difference of opinion so the outcome can benefit future questions too.