Why does user feedback need to happen on the same channel as new content notifications? In my mind keeping a distinction is a huge advantage because it puts the creator in charge of how they interact with their audience.

They could add a comment section to their WordPress blog. They could cross-post to Reddit. They could have an email dedicated to comments and feedback. They could do none of those things because they really don't care what the audience thinks.

Because RSS/Atom doesn't integrate two-way interaction, there are no preconceived notions of how the second direction ought to work.