alt Hacker NewsThis. And also a lack of respect for people commenting about it.
I used to randomly evaluate and give honest feedback on invisible projects when I had the time. Most times I was completely ignored, even when I was the only person who really cared enough to answer. Eventually, I got bored.
I've had similar experiences, but also good experiences where the person reached out/replied and we had a conversation.
I suspect for some of the non-engaging posts it's just throwing it out there, inexperience or part of the product hunt playbook