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.
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.
You are describing Postbacks: https://en.m.wikipedia.org/wiki/Postback
I don't think this Wikipedia page is describing the thing you think it is. Maybe it's the wrong link?
He's probably thinking about: https://en.wikipedia.org/wiki/Pingback
I think you're right.
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.
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.
[1] https://havenweb.org/2023/04/10/private-comments.html