I also find Product Hunt to be alienating and therefor a bad overall experience. I understand wanting to limit who can post new submissions at first, to avoid too many self promotional posts, but I don't understand the rationale behind preventing users from commenting. It's especially perplexing because the quality of comments on Product Hunt is pretty low right now so I'm not sure what you're even protecting. There are a lot of comments that don't add any value to the conversation, that say little more than "Thanks" and "Great job!", and hardly ever any substance filled replies. If you're worried about spam, I would think putting new commenters into a moderation queue until they've proved themselves to be worthy contributors would be an easy enough solution.

I love Show HN posts so I should be one of your biggest fans. I want to be. I love reading about new products and I love discussing them. But every time I visit your site I feel like I'm treated like a second class user. I wonder how many others feel the same.

EDIT: I do think Product Hunt will be a successful venture for you. It's a decent idea but more importantly you're hustling hard to build a community, which is no easy task. Most developers tend to put in a lot of hours building something scalable but are too far outside their comfort zone when it comes time to find and engage with users. That's something you're excelling at and I think it's the reason Product Hunt will ultimately succeed. I just think you're making a mistake with some of your earliest adopters. You should be treating us as if we're special, because we are. Instead you're asking us to be a part of your community but barring our ability to communicate.