Manual:$wgRestrictDisplayTitle

Parser: $wgRestrictDisplayTitle
Restrict {{DISPLAYTITLE}} to titles that normalize to the same canonical database key
Introduced in version:1.14.0 (r39552)
Removed in version:Still in use
Allowed values:(boolean)
Default value:true

Details

Restricts display titles to titles that normalize to the same canonical database key as the real page title. This roughly means that only capitalization variations of the title are accepted. If set to false, any display title is allowed. This is not recommended however, as it breaks the wiki convention that a page's title is its name, and thus can be used for linking to it.

MediaWiki version:
1.22

Additionally, some inline CSS rules like display: none; which can cause the text to be hidden or unselectable are disallowed.

See also