Will think about that, what kind of things would you put? I don’t want to become a CMS or geo cities :)

It's mainly to work around bugs in the system. For example:

site: https://www.shawwn.com/thanks

markdown: https://www.shawwn.com/thanks.page

If you "view source" on the markdown page, you'll see:

  Twitter: <a href="https://twitter.com/theshawwn">@theshawwn</a>  

The reason is that [@theshawwn](https://twitter.com/theshawwn) didn't convert into HTML for some reason. I assume the @ character threw it off, and I didn't want to drop what I was doing to figure out why. But there are a million small things like that.

For https://collectednotes.com/shawwn/sample-note, I would put GA into my notes.

It works for me: https://collectednotes.com/blog/twitter-usernames

See markdown: https://collectednotes.com/blog/twitter-usernames.md

Yes, your markdown implementation is fine. Pandoc (the one I use) seemed broken. The HTML was a way of working around the problem.

The main reason to let users inject HTML is that they can add features you don't have. GA is one; mathjax is another.