YC Hacker News Comments is a Chrome add-on developed by Ivan Novikov. This free browser extension provides users with the number of Hacker News comments for the current tab.

When browsing a page that has been linked on Hacker News, the toolbar button of YC Hacker News Comments displays a badge indicating the number of comments. By clicking on the button, users can open the comments in a new tab. In cases where the page hasn't been posted on Hacker News, the button will open the "submit" page with the URL and title pre-filled.

It's important to note that the badge is not updated in real time, but only when the URL changes. YC Hacker News Comments also considers multiple linking pages on Hacker News and displays the one with the most comments. Additionally, the extension ignores the URL fragment when searching for the referencing Hacker News page.

Overall, YC Hacker News Comments is a handy Chrome add-on for those who frequently visit Hacker News and want quick access to the comments section.