Manual:$wgCapitalLinkOverrides

Details
Per namespace configuration for $wgCapitalLinks.

Some special namespaces (such as Special, User, Mediawiki, and their associated talk namespaces) must be true by default (and setting them has no effect), due to various things that require them to be so. Also, since Talk namespaces need to directly mirror their associated content namespaces, the values for those are ignored in favor of the subject namespace's setting. Setting for NS_MEDIA is taken automatically from NS_FILE.

Example: