The problem of changing messages given by software, and making it easier to translate the software into other languages, has been around for a while. I wrote some code to allow wfMsg() to access the database, and on September 1, Brion wrote:
Another possibility is to make [[Special:xxx]] just appear a little more like a normal page; that is, there would be an "edit this page" link by which you can edit the header text.
So instead of a separate [[Wikipedia:Recentchanges]] to find and maintain, you'd just go to [[Special:Recentchanges]] and hit edit in the usual fashion. A [[Special talk:xxx]] namespace to go with it would be useful too.
Now this is a nice idea, but IMHO main problem with it is that some special pages have many different text messages, and some text messages which we want to customise are not on special pages (e.g. deletion).
I propose creating a new namespace "MediaWiki:" as namespace 8, with a "MediaWiki talk:" namespace as #9. This namespace would contain a page for each message in Language.php, plus categorisation and miscellaneous related pages. Clicking on "edit this page" in a special page (or deletion, etc.) would take you to a page in the MediaWiki namespace determined by the local language. In most cases, I imagine that page would be a list of links to customisable messages, with edit links for convenience. For the benefit of special pages where there is only one customisable message, some "edit this page" links could go straight to an edit page.
All the help pages should stay in the Wikipedia: namespace. The MediaWiki: namespace should be reserved for pages which directly affect the functioning of the software, and closely related information. [[Wikipedia:Recentchanges]] and [[Wikipedia:Book sources]] should be moved to MediaWiki:.
Using the name "MediaWiki" avoids the technical difficulties associated with using "Special" for two different purposes. It also brings more prominence to the new name of our software. At the moment, most editors still just call it "the software" or "the PHP script". Using the existing "Wikipedia" namespace would clutter it up with hundreds of small articles, most of which are of no interest to editors or readers.
Some messages may need to be protected. Many messages currently require raw HTML. There's no need to change that in a hurry, as long as the user is informed of the issues. Unfiltered HTML messages should certainly be protected, to avoid security problems.
-- Tim Starling <t(starling_physics*unimelb^edu!au>