For some unknown reason, the settings of quotes in jgm/citeproc/locales/zh-CN.xml and (originally) citation-style-language/locales/locales-zh-CN.xml is:
<!-- PUNCTUATION -->
<term name="open-quote">《</term>
<term name="close-quote">》</term>
<term name="open-inner-quote">〈</term>
<term name="close-inner-quote">〉</term>
<term name="page-range-delimiter">–</term>
which will convert “” into 《》 in titles of the citation, e.g. “软色情”，正在榨干这一代的年轻人 -> 《软色情》，正在榨干这一代的年轻人.
Temporary fix: add
lang: en
in the metadata of markdown files, i.e.
---
lang: en
mainfont: simsun.ttc
bibliography: [ref.bib]
---
# Heading 1
...