I don't know if this is a feature already, but i don't find it right know, so i go the lazy way and ask.
Some pages in the template namescape are not supposed to be transcluded directly on articles (e.g., they are parts of another templates, documentation subpages). There should be some kind of magic word that when is present on a page, the template selector on Visual Editor don't show them.
See also
A set of categories will do better than a magic word. In de.wp, documentation templates are in the category Kategorie:Vorlage:nur Dokumentation.
See http://imgur.com/UciVLHL for a screenshot that shows (with red dots) a list of pages in the Template: namespace that shouldn't be transcluded (directly; some are meta templates). It would be nice if these could be filtered out of the search results somehow.