HN does not often add new features. I assume this is the main reason HN has not added Markdown.

I would prefer that HN continues to NOT support Markdown. After all, the entire point of Markdown is that it should be readable in its unprocessed form [1]. Therefore, Markdown obviates its own utility: Why not just present the source text of a comment as-is? Why confuse non-savvy users with behaviour like collapsing line breaks [2]?

[1] "The overriding design goal for Markdown’s formatting syntax is to make it as readable as possible. The idea is that a Markdown-formatted document should be publishable as-is, as plain text, without looking like it’s been marked up with tags or formatting instructions." https://web.archive.org/web/20040402182332/https://daringfir...

[2] https://news.ycombinator.com/item?id=22677936

As implemented in most places, Markdown does many unexpected things to user text. e.g. changing numbers in lists, breaking some urls, breaking textart.

If one commenter wanted to get attention for their comment, they’d overuse large headings and bold. A lot of Markdown’s value comes from consistent use throughout a document (here, all comments).

I guess it's for historical reasons. Markdown wasn't really that popular before GitHub made it popular. Hacker News is older than GitHub.

HN does implement Markdown to some extent, such as lists, italics, quotes, code blocks, etc.