The graph is from: https://track-hacker-news.com/
EDIT: This is the post referenced: https://news.ycombinator.com/item?id=46512881
2) Flame-War Detector ("A good rule of thumb for this effect is when the number of comments on a submission exceeds its score.")
Quotes from here: https://github.com/minimaxir/hacker-news-undocumented