User blog comment:DaNASCAT/Update Your CSS and JavaScript To Speed Up Your Wiki/@comment--20120831160603/@comment-5209426-20120901085033

The thing is, he did fix 'w:c:wiki:Article' so that it works the way we would expect it to (site subdomain, w:c:onepiece.risposte:MediaWiki:Common.js)... but then decided that we should all prefer to use 'url:' instead even though it does the same thing and is a unique syntax that doesn't look like an interwiki link.

In any case, 'w:c:' does work (after the update hits on Wednesday) so you can use it, just that the help page isn't going to tell you that for some reason.

[BTW, 'url:' is already part of the current live code, so it works right now. That might be why ('w:c:' is broken until the patch goes live, 'url:' works right now)]