Manual:$wgDebugRedirects/ja

詳細
This appears to help you know when a redirect is happening. If you set this to a value in your, then any time a "redirect" happens, you get stopped at the point the redirect begins by ending on a page that simply says "Location: " and after that is the URL that you are being sent to. It does not do the redirect automatically.

この設定は、HTTP リダイレクトのデバッグ用です. これは、記事の通常のリダイレクトには影響しません. (An example of a redirect it would affect would be capitalizing the first letter of an article, or localizing a special page name, provided you accessed the non-canonical form directly from a URL.)

If you search for $wgDebugRedirects in the source code, and don't find it, try searching for $config->get( 'DebugRedirects' ), which occurs in includes/OutputPage.php (at least in MediaWiki 1.28).