[loop22]

> I wish there was some kind of service or plugin (preferably not based on a centralized service) where one could easily leave comments on any site even if the site itself did not support comments.

IIRC the Dissenter extension was just that, albeit centralized.

[vvatermelone]

There's an extension called Epiverse that does something similar. It used to have its own comment sections like Dissenter, but has since shifted to just showing discussions on reddit/HN that point to the webpage you're currently on. It's actually how I discovered HN.