I’m not sure I understand why this is a problem. RSS is a spec for publishing a list of available content, or publishing the content directly. Formatting that content was always going to be something people wanted to do, so whether it was rich text, html or what became markdown, it was inevitable that aggregators were always going to have to deal with both publishes wanting their publication to have styles and users wanting their aggregator software to either handle that style or hide it.

At least with a cdata tag your being explicitly told “here be dragons”