Steps to replicate the issue (include links if applicable):

• Open any page in the main namespace of nl.wiktionary using the legacy Vector skin, e.g. proscriptie

What happens?:

• The TOC shows headers in the form <i>header text</i>. Screenshot:

Additional information

• nl.wiktionary uses headings that are in italics, using templates with '' in wikitext.
• the headings are created by our template {{-pron-}} ( source: https://nl.wiktionary.org/w/index.php?title=Sjabloon:-pron-&action=edit ):

=====''[[WikiWoordenboek:Uitspraak|Uitspraak]]''=====<noinclude>
[[Categorie:Lemmasjablonen|pron]]</noinclude>

And the rendered HTML is:

<div class="mw-heading mw-heading5" id="mwRA"><h5 about="#mwt2" typeof="mw:Transclusion" id="Uitspraak" data-mw="{&quot;parts&quot;:[{&quot;template&quot;:{&quot;target&quot;:{&quot;wt&quot;:&quot;-pron-&quot;,&quot;href&quot;:&quot;./Sjabloon:-pron-&quot;},&quot;params&quot;:{},&quot;i&quot;:0}}]}"><i><a rel="mw:WikiLink" href="//nl.wiktionary.org/wiki/WikiWoordenboek:Uitspraak" title="WikiWoordenboek:Uitspraak">Uitspraak</a></i></h5></div>

But in de TOC it is rendered as &lt;i&gt;Uitspraak&lt;/i&gt;

• This bug was reported this morning by a user usually contributing every day. I myself use the new Vector skin, but I was able to reproduce the error when using the old skin.

What should have happened instead?:

• The items in TOC should be shown in italics, without tags

Software version (on Special:Version page; skip for WMF-hosted wikis like Wikipedia):

Other information (browser name/version, screenshots, etc.):

• The bug is visible in Firefox and Chrome.