I have been using Hacker News for almost 15 years and saw the evolution of both threads over this period.
Who is hiring? thread used to be about personal recruiting and opportunities posted by individuals who were also engaged here. For example, I met a founder who previously went through YC batch and also a VC who was recruiting for one of his portfolio company, through this thread.
Now, the "Who is hiring?" thread has degraded into just another "impersonal" source of potential candidates, like LinkedIn, Indeed and other job boards, and/or being used for market exposure to target audience. Postings from personal and/or engaged accounts have dwindled to almost none.
IMO, you are likely to have better experience if you ignore postings that redirect you to career page to apply and postings from new accounts and/or accounts that do not actively engage in the community.
Who wants to be hired? thread seems to have had several incarnations, over the years, for people looking for job and or project. I regularly post to this thread and routinely get contacted, mostly by wannabe entrepreneurs who want people to work for free/equity only or recruiters. But I am not a traditional job searcher.
I received two paid engagements through this thread, primarily through direct contact by founders. First one was a pre-seed incubator startup that engaged me for a pilot with a potential customer. We parted ways after successful engagement in few months as I didn't want to move back to US and for long-term effectiveness with targeted vertical, a US based person would have been better fit. Actually, later I also participated in their seed round and with excellent outcome till now. The second one (latest) was a seed funded startup that engaged me for a PoC with a large Japanese company, which turned out be a very bad fit with poor culture and poor communications. They still haven't paid me for the time I worked with them.
I have also made good connections with a few fellow posters on this thread. I generally reach out to posters on this thread whose profile I find interesting.
IMO, if you focus on contacts by people who are engaged in community, you will have better experience. Now, I generally ask for HN username as a first step. Also, don't work for free, timely exchange of any money is a good indicator of character.