The line of code
: √ [[the]] {{x|en|moon|el=luna [[satelles]] [[terra]]e [[sum|est]]|en=[[the]] [[moon]] [[be|is]] [[earth]][[-'s|'s]] [[satellite]]}}; {{x|en||ni=x|nn=x|el=[[Mars|Marti]] [[duae]] [[luna]]e [[sum|sunt]]|en=[[Mars]] [[have|has]] [[two]] [[moon]]s.}}
Link to relevant template: https://la.wiktionary.org/wiki/Formula:x
HTML Output:
<dl><dd> √ <a href="/wiki/the" title="the">the</a> <span lang="en" class="lang-en" dir="ltr">'<i><a href="/wiki/moon" title="moon">moon</a><b></span> <span lang="en-Latn" class="lang-en-Latn"></span> <span class="noprint" title="Dictio in suae linguae Victionario descripta."><a href="https://en.wiktionary.org/wiki/moon" class="extiw" title="en:moon">☞<span style="font-size: 50%; vertical-align: super;">en</span></a></span> — <em lang="lang-en" dir="ltr"><a href="/wiki/the" title="the">the</a> <a href="/wiki/moon" title="moon">moon</a> <a href="/wiki/be" title="be">is</a> <a href="/w/index.php?title=earth&action=edit&redlink=1" class="new" title="earth (non est haec pagina)">earth</a><a href="/wiki/-%27s" class="mw-redirect" title="-'s">'s</a> <a href="/w/index.php?title=satellite&action=edit&redlink=1" class="new" title="satellite (non est haec pagina)">satellite</a></em>, “luna <a href="/wiki/satelles" title="satelles">satelles</a> <a href="/wiki/terra" title="terra">terrae</a> <a href="/wiki/sum" title="sum">est</a>”; <span lang="en" class="lang-en" dir="ltr">'</b></i></span> <span lang="en-Latn" class="lang-en-Latn"></span>  — <em lang="lang-en" dir="ltr"><a href="/wiki/Mars" title="Mars">Mars</a> <a href="/wiki/have" title="have">has</a> <a href="/wiki/two" title="two">two</a> <a href="/wiki/moon" title="moon">moons</a>.</em>, “<a href="/wiki/Mars" title="Mars">Marti</a> <a href="/w/index.php?title=duae&action=edit&redlink=1" class="new" title="duae (non est haec pagina)">duae</a> <a href="/wiki/luna" title="luna">lunae</a> <a href="/wiki/sum" title="sum">sunt</a>”</dd></dl>
Apparently Malformed as it's turning a '''<content>''' rule into <i><content></b> instead of
<b><content></b> which is causing tags to be mismatched.