HN is indexed in effectively real time as well. I've googled several phrases I've read here, hoping to find more information, where the HN comment of interest is the sole result.
I just had the opposite happen, was looking for a post I know ive found through google before and had to go through bing and then yandex to find it. Google's historical archive of hn appears wonky, or at least did that day.
This spooked me the other day. Made a comment about a phenomenon I knew of and the name I knew it by. Got curious whether other people knew it by that name too, googled the name, and the top result was my own comment made just a few minutes ago.