https://addons.mozilla.org/en-US/firefox/addon/hacker-news-comment-highlight/ https://addons.mozilla.org/en-US/firefox/addon/hacker-news-c... This addon keeps

https://addons.mozilla.org/en-US/firefox/addon/hacker-news-comment-highlight/ https://addons.mozilla.org/en-US/firefox/addon/hacker-news-c... This addon keeps track of which comments you've seen in a given Hacker News thread, and then highlights the new comments when you return to the page.