Danny has set up closed forums for quite a few of the companies. If you really want a closed forum for instructors why don't you ask him to set one up. All the time it is an open forum, I don't see any harm in any of us posting to it.
Where else can these questions be asked? if you don't want to answer pupils (or PPLs) questions, refrain from opening threads that end in a question mark. There are plenty of knowledgable folk only too happy to help someone out.