One thing I wish I could easily augment with RSS is the ability to send and discover webmentions. I would love to read something in my RSS feed, respond to it, and post a webmention back to the original author. I'd also like to be able to see in the RSS feed what other pages have posted webmentions to the page I'm reading.
I have opinions[1] on Webmentions. It sounds like such a great approach, but it also opens up the original author to hosting mountains of spam and other low-quality comments, and moderation is a lot of work. Arguably, we see the same problem today on sites that let you post comments.
What you're referring to @j2kun is named a *social reader*. See: https://indieweb.org/social_reader I'm sure there other examples of software/clients besides those portrayed on indieweb.org too.
It's a shame that this was so vulnerable to abuse. Webmentions as a concept is such a great idea. Maybe the more recent implementation is better, but it doesn't seem like many people (relatively speaking) are familiar with the idea.
