Atom has support for commments. Decentralized blog comments work like this: You post a reply to your own blog and set rel=“in-reply-to” then notify the author using Webmention. The authors blog software then adds the comment, which gets included in the feed. See aaronparecki.com for working example and the IndieWeb community in general for an example of a community doing standard decentralized comments on the web.
RSS has <wfw:commentRss> for linking comments feed and <comments> for linking page with comments. Atom has <link rel=replies> or just <link rel=alternate type="application/atom+xml"> for comment feeds.
And I'm visiting blog post pages first to check whether they have Disqus comments (which processed separately via Disqus API) and <blog_post_URL>/feed feeds.
The future of the blogosphere remains bright.