There is also https://lobste.rs, and I like their approach more (it's not inherently related to venture capital backed startups, and its much more transparent with the community (i.e. the concept of effectively hiding unpopular opinions does not exist there)

Unfortunately, it's also nowhere near as active - possibly because it works on invites and its often hard to find someone who will invite others.

Having said that, if anyone wants an invite, please reply here (or see my profile to email me, please include your HN username if you do that) and I'll shoot you an invite.