Has HN added new blocking mechanisms, if so why, and how do they work... and more generally, why is blocking VPN IPs becoming more common?
The standard excuse I've heard before is "VPNs are a larger source of abuse". I take issue with this reasoning in that firstly: it lacks a denominator, VPNs are a larger source of traffic in general, abuse should be considered as a ratio. Secondly, VPNs are a known highly NATed collection of IPs, so lots of legitimate users will be thrown under the bus in the same stroke.
These arguments usually fall on deaf ears with most site owners who do not care about user discrimination, and will reach for the easiest blunt tool rather than make their service more fundamentally resilient. I expected more from HN though.
I'd be happy to help you, but for that you should follow the site guidelines and ask us at hn@ycombinator.com instead of jumping to conclusions and posting riler-upper threads.
Have you contacted hn@ycombinator.com because Dang is very responsive and helpful, despite it being a very demanding job running HN. Dang should be praised rather than criticized for the wonderful job he does.
Why do you assume they don't do this and that VPN traffic doesn't have a much higher rate of abuse? Having significant legitimate traffic and a much higher rate of abusive traffic are not mutually exclusive.