I'd be careful about making historical claims (let alone calling names like "blatant ripoff") unless you're sure you're on solid ground. pg gave Steve and Alexis the idea for Reddit and was their biggest influence. Reddit's and HN's designs are similar because they came from a common source. pg has in fact said what that source was: delicio.us/popular: https://news.ycombinator.com/item?id=903365
https://web.archive.org/web/20051220094850/http://del.icio.u...
The Reddit guys confirmed that in interviews. For example: https://mixergy.com/interviews/no-reddit-didnt-copy-digg-her...
Similar story here: https://www.vanityfair.com/news/2018/09/how-steve-huffman-an...