Kiwi Conversations is a free Chrome extension that analyzes forums, chat forums, comment threads, and social networks for conversations about the site you're on. Once you find them, it automatically searches for the best, newest, and most relevant threads, posts, and comments.

Features:

Kiwi uses third-party APIs (Reddit, Algolia for HN, Product Hunt API [with Algolia Search for custom string searches] and Google News) to provide conversations about the URLs you are visiting while you surf.

The only way you can use the extension is by first clicking the green “Research this Url” button while you're visiting a URL. After that, you can set a specific URL that it should check for conversations.