Ah welcome to HN. This particular etiquette is oddly not covered in the guidelines but instead in the FAQ:
> How do I make a link in a text submission?
> You can't. This is to prevent people from submitting a link with their comments in a privileged position at the top of the page. If you want to submit a link with comments, just submit the link, then add a regular comment.
> How do I make a link in a text submission?
> You can't. This is to prevent people from submitting a link with their comments in a privileged position at the top of the page. If you want to submit a link with comments, just submit the link, then add a regular comment.
https://news.ycombinator.com/newsfaq.html