Wikimedia developers wikitech-l@Wikipedia.org writes:
Additionally, I really don't think it should be possible to include any article in any other article. An article should be clearly marked as being "includable" (which it is by being in the MediaWiki namespace). I don't know if it is currently possible to place a {{msg:}} inside a page on the MediaWiki namespace, but I believe that should be disallowed to prevent circular references (infinite recursion).
If you did implement this feature, as you build up the page you *would* have to watch for circular references. You could do this by stacking the fully qualified names of what your in the middle of including and make sure the new file isn't already on the stack.
You should really do this anyway if there is nested inclusion now.
Marking an article as includable is a thought, but how would you do that? You could restrict your inclusion to a special "Templates" name space, but that would not be as powerful. I don't think that would be necessary, unless there are caching considerations.
Nick Pisarro