A check using just about any wiki-page against w3.org's HTML Validator (new Alternative site) reports an error for the <link> tag being generated for what appears to be any position: bottom loaded module(s).
For Example: verifying against https://test2.wikipedia.org/wiki/Testpage1 reports
Error: Element <link> is missing required attribute - property. From line 184, column 1; to line 184, column 159 <link rel="stylesheet" href="//test2.wikipedia.org/w/load.php?debug=false&lang=en&modules=ext.wikimediaBadges&only=styles&skin=vector&*" />
Going by the specs for the link element, it seems rel= needs to be replaced by itemprop= when the link element in question appears outside of the HEAD element where it is typically found but is generated somewhere in the BODY element instead.