PS D:\admin> go version
go version go1.15.6 windows/amd64
PS D:\admin> hugo version
Hugo Static Site Generator v0.80.0-792EF0F4 windows/amd64 BuildDate: 2020-12-31T13:37:57Z
If others managed to render the <sup> tag, with the above Goldmark configuration, as discussed in the topic you linked to above and you cannot get it working, then you will have to share your project for us to see what is going on.
I can’t find that file in your repository.
Also: It appears you are using an IntelliJ project per content subfolder. These .idea subfolders should only exist at the root level. This is probably not connected, but might lead to other issues.
These bold text are exactly same in markdown file.(Never mind about mathjax error. I can handle this.)
I guess that these are occurred by same reason. In my first screenshot also, even bold texts are not rendered. I can give up using superscript, but bold text issue is quite critical to me.
**1.** 핵막이 없는 생물을 **원핵 생물[^Prokaryotes]**이라 한다.
<!-- footnote ok, not bold -->
**2.** 핵막이 있는 핵으로 이루어진 생물을 **진핵 생물^Eukaryotes^**이라 한다.
<!-- footnote not ok, not bold -->
진핵 생물에서는 유전 물질을 지니는 부분인 **세포핵[^Nucleus]** 과 각종 대사가 일어나는
<!-- footnote ok, bold ok -->
[^Nucleus]: foo
[^Prokaryotes]: bar
[^Eukaryotes]: baz
So, to clarify, you are asking about using superscript notation? Not about footnote superscript rendering?
Superscripts are not part of the CommonMark spec, which is why in the topic you link to, the poster is using <sup>foo</sup>, and unsafe to render raw html in markdown.