Manual:$wgUseTrackbacks

Details
$wgUseTrackbacks enables blog-style trackback support if set to true in. When MediaWiki receives a trackback ping, a box will show up at the bottom of the article containing a link to the originating page. The link format can be customized by editing MediaWiki:Trackbackexcerpt.

However, MediaWiki does not support sending trackback pings.

Form MediaWiki version 1.18 to 1.19 one also needed to assign relevant user groups the "trackback" right to enable this feature.