There is Zeeker <https://addons.mozilla.org/en-US/firefox/addon/zeeker/>, but there seems to be no new versions recently, and I cannot find a link to the browser add-on on their web site, so they might have abandoned it.

There was also “Dissenter”, still available at <https://github.com/gab-ai-inc/gab-dissenter-extension/releas...>, but the website seems to have pivoted to something else, and the add-on seems to have been removed from the official add-on repositories (possibly due to negative press coverage: <https://archive.fo/sWxAS>). Further discussion: <https://discourse.mozilla.org/t/the-removal-of-the-dissenter...> and <https://www.reddit.com/r/browsers/comments/ptaau2/what_happe...>

I purposely installed a browser plugin that removes comment sections from web sites. I really don’t know why anyone would want to add one.

The problem with comment sections on web sites is that the web sites are incentivized to have shitty comments for engagement and ease of moderation. If it's a browser plugin, it's out of the website's hands and as the user I could probably configure it so I only see comments from people I think are good at commenting, like my friends or people I follow on social media.

I think it was to be able to discuss things on websites that removed comment sections or that had a lot of heavy moderation that prevented meaningful discussions.

I feel like this existed in the 90's; Basically a web browser where every page was a chat room. Maybe I'm confusing it with ThePalace or WorldsChat.