Do you remember #Dissenter, Gab's short-lived attempt at creating a decentralised commenting system, that despite its practical applications, was removed from the Chrome web store?
https://reclaimthenet.org/dissenter-free-speech-browser
Nostr fixes this.
I recently submitted a feature request to #Amethyst for a fully Decentralised Commenting System on their app. If fully implemented, it would would give users the ability to comment on and follow others' comments about any web resource on the internet.