It is very powerful to be able to say: “my Show HN post was at #1 for over 12 hours”. [1] It tells potential funders/partners that your idea is very popular in a community that they respect.
I have also found a couple important partners through HN. In December, I was deep in a thread when I saw a comment mentioning an extensible iOS browser that a YC company was soon to launch. [2] I reached out and they’re now one of our partners. Ditto for a popular podcast website. [3]
HN has a lot of visitors who are willing to embrace new things, and who are fast-moving. This can be very valuable if you’re looking for early adopters and partners.
1: https://news.ycombinator.com/item?id=6335784