“some reasonable content cannot reliably be expressed in RSS, whereas it’s unambiguous in Atom”
Most Atom versus RSS arguments are taste. This one is not. RSS never says whether a title is plain text or HTML, so every reader guesses and some titles come out wrong forever. Atom’s text construct just declares it. The catch is podcasts, where the big syndicators still only speak RSS because Apple picked it first and nobody has been willing to eat the migration. Twenty years of ambiguity preserved by one company’s default.