Ask HN: Why HN doesn't have a search function?

It does. Look at the bottom of the footer.

Algolia search at the bottom of the page is pretty good. Use a site: search via Kagi/Google if you want to keyword search comments though

You’ll probably get better results if you use Google to search the site

They have. Scroll down.

when you search for "recession" Algolia search even matches recursion. Its not good enough for searching