I think @fiatjaf has written a nostr app (Browser plug-in) for this: https://github.com/fiatjaf/wen

There's also has a nostr-based disqus-like plug-in that can be integrated to any Web page, and fj uses it on his blog.

Also, on a related note, Gab was the first to introduce the idea with "Dissenter," but it was eventually banned from the Chrome store...