I've been a Wikipedia trainer at schools for quite some time now. Probably the single most common mistake people in my workshops make when accessing a Wiki's meta pages (i.e. "Wikipedia:Help") is by omitting the colon indicating the namespace.
The default search namespace is just NS-0, i.e. the main namespace. This means if you enter "Wikisource Help" on en.wikisource.org, you get nothing useful: http://en.wikisource.org/w/index.php?search=Wikisource+Help&button=&...
English Wikipedia has implemented a workaround by creating redirects from the main namespace to the project namespace: an ugly fix, since it mixes up the distinction between namespaces.
Instead, we should make MediaWiki a bit smarter with regard to the namespace selection: When you search for "Help Editing", the Help namespace should be included.
This could be done in the most simplest form by checking whether a namespace string is a prefix of the search string (perhaps excluding exotic namespaces such as MediaWiki) or even if the namespace name is contained in the search string.
What do you think?
Best regards, Tobias