A somewhat cleaner diff:

• https://zh.wikipedia.org/w/index.php?title=%F0%B0%9A%BC&diff=76206218&oldid=76206215&diffmode=source

Which is presently the latest version, aka the same as:

• https://zh.wikipedia.org/zh-cn/%F0%B0%9A%BC

But note that

• https://zh.wikipedia.org/zh/%F0%B0%9A%BC

(aka the "no conversion" output) seem to appear correctly.

The display title is generated by a template invocation {{全局僻字|𰚼|⿹气云}} whose expansion is:

• https://zh.wikipedia.org/wiki/Special:ApiSandbox#action=expandtemplates&format=json&title=%F0%B0%9A%BC&text=%7B%7B%E5%85%A8%E5%B1%80%E5%83%BB%E5%AD%97%7C%F0%B0%9A%BC%7C%E2%BF%B9%E6%B0%94%E4%BA%91%7D%7D&prop=wikitext%7Cproperties&formatversion=2

This is a quite-complicated invocation of the -{T|...}- language converter rule, which sets the display title, followed by an -{H|...}- unidirectional rule, presumably intended to affect the result of the page (see https://zh.wikipedia.org/w/index.php?title=Template:%E5%85%A8%E5%B1%80%E5%83%BB%E5%AD%97&action=edit ) and that latter rule appears to be "corrupting" the display title somehow, primarily by being a <span> tag which, instead of being stripped from the display title (9f14fbd002713abcf65a5b5cddc5d52dee90a977) is instead being HTML-escaped and included as literal text.

(T26072 is a much older but perhaps related bug, although it was apparently fixed back in 2010.)

Change 894746 had a related patch set uploaded (by C. Scott Ananian; author: C. Scott Ananian):

[mediawiki/core@master] WIP: Don't clear LanguageConverter display title when converting ToC

https://gerrit.wikimedia.org/r/894746

It turns out that this issue *is* related to T306862, via a side-effect of calling LanguageConverter::convertTo(). The linked patch above describes the situation in its commit message.

Change 894746 merged by jenkins-bot:

[mediawiki/core@master] Don't clear LanguageConverter display title when converting ToC

https://gerrit.wikimedia.org/r/894746