Thing is, if people wanted you to leave comments, they would add comments. Every CMS worth its salt has this feature out of the box, and even static websites can add the likes of Disqus in seconds.
This "solution" is already here in the form of traditional social media like Twitter, Facebook and Reddit if people want to provide any additional context or commentary.
The problem with solutions like these is the potential for abuse, and somebody needing to moderate it ultimately if it ever does catch on in any meaningful way. At that point, you may as well just use an on-site comment section and let people deal with their own problems, and it's already decentralized, and a choice that people can make for themselves rather than having what's effectively graffiti showing up via a browser extension when people land on their site.