It's better to focus on the content than the medium (pun intended, as usually this kind of comment are usually when people post something on medium, as if they didn't have another copy of their post backed-up somewhere else.)
But I'll bite: What's wrong exactly with using Github's markdown renderer?
This is a plain markdown file, the author could host it on S3 and it'd look like:
There are a ton of markdown renderers, author could write one in a few hours for the feature used (#, ##, ###, >, and unordered lists), or even better, paste the thing in one of the many markdown-to-html tools (https://markdowntohtml.com/).
This is not like the author used some proprietary syntax, that only displays on Github.
The author isn't in control of the chrome around it. It becomes an advertisement for the proprietary service. You can slap Markdown through Pandoc and host statically somewhere where you do control the the chrome. This is a similar objection to say Medium, but Medium authors aren't usually developers and don't have the know-how.
GitHub has forked Markdown in a way that is incompatible with CommonMark, GitLab, etc. So the author might accidentally buy into that fork which there is no quality control for (just look at the lack of care put into their attempt at admonitions).
But I'll bite: What's wrong exactly with using Github's markdown renderer?
This is a plain markdown file, the author could host it on S3 and it'd look like:
https://gist.githubusercontent.com/evadne/c9aeca424d30f024ba...
There are a ton of markdown renderers, author could write one in a few hours for the feature used (#, ##, ###, >, and unordered lists), or even better, paste the thing in one of the many markdown-to-html tools (https://markdowntohtml.com/).
This is not like the author used some proprietary syntax, that only displays on Github.