For previewing the body text of posts, I'm not sure how one should otherwise display the text when confined to the list layout of feeds. For example, rendering the html generated from the markdown could lead to some irregularly sized preview text blocks, line breaks, font sizes, given the headings you mentioned would throw off the minimalism.
That said, I would like to see at least the markdown hyperlinks rendered inline with the body text preview, as the URLs often take the majority of the limited character count, and could be more compact as clickable links to enable more contextual text to be included in the summery. Then again, I'm not sure how embedded images using markdown could be rendered without yet again borking the structured layout of the aggregated feed. Raw text seems to have been a practical compromise that would be robust to gaming or clickbaiting in body text previews.