At http://parsoid-lb.eqiad.wikimedia.org/enwiki/Japan_at_the_2012_Summer_Olympics?oldid=600210359 I observed content leaking out of a template.
The wikitext for the reference in question is:
<ref name=JAAF20120611>[http://www.jaaf.or.jp/fan/news/2012/20120611.html {{Nihongo||ロンドンオリンピック トラック・フィールド種目・競歩種目の日本代表選手|The Japanese national team of Track & Field and Race Walk at the 2012 Olympic Games}}] {{ja icon}}. Japan Association of Athletics Federations (2012-06-11). Retrieved 19 June 2012.</ref>
The resulting Parsoid HTML (cleaned up and indented for readability) is:
<li about="#cite_note-JAAF20120611-7">
<span rel="mw:referencedBy" data-parsoid="{}">...</span> <a rel="mw:ExtLink" href="..."> <i about="#mwt199" typeof="mw:Transclusion" data-mw="..."> The Japanese national team of Track & Field and Race Walk at the 2012 Olympic Games </i> <span style="font-weight: normal" about="#mwt199"> <span typeof="mw:Entity"> </span> ( <span class="t_nihongo_kanji" lang="ja"> ロンドンオリンピック トラック・フィールド種目・競歩種目の日本代表選手 </span> <sup class="t_nihongo_help noprint"></sup> </span> </a> <a rel="mw:WikiLink" href="..." data-parsoid="misnested"> <span class="t_nihongo_icon" style="..." data-parsoid="misnested"> ? </span> </a> ) <link rel="mw:PageProp/Category" href="..." data-parsoid="misnested"> <span class="languageicon" style="..." about="#mwt137" typeof="mw:Transclusion" data-mw="..."> (Japanese) </span> <link rel="mw:PageProp/Category" href="..." about="#mwt137"> . Japan Association of Athletics Federations (2012-06-11). Retrieved 19 June 2012.
</li>
Note that all of the elements that have data-parsoid=misnested on them were generated by the template, but were not part of the template's about group or marked in any other way as having been template-generated. This means that if the user edits the reference (or a bug in VE causes a whitespace edit, see bug 69861), you'll get a dirty diff that expands the second half of the template, like https://en.wikipedia.org/w/index.php?curid=31216768&diff=621842944&oldid=600210359 .
The core of the problem seems to be that {{nihongo}} was used inside of a link, and the template outputs a link itself (a linked, superscripted question mark linking to a help page), so Parsoid was asked to put a link inside of a link and tried to clean that up. Unfortunately it looks like this misnesting cleanup loses template information.
Version: unspecified
Severity: normal
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=69861