When I saw this, I thought it was a paid advertisement on HN. yuck. At least when other companies do the jobs post it always includes "is hiring" to make it clear what it's for.
Some YC companies have more creative/curiosity gap titles for their hiring ads, which I dislike. There was once a job ad which was just a terminal command that pulled their job information, which was one of the few times I had to email hn@ycombinator.com to suggest that HN not encourage users to run arbitrary code.
I could be wrong, but I thought the "is hiring" posts are from a mechanism specifically for Ycombinator companies (which is why they also don't have comments on them)