Rich text without regret

Rich text is where layout sneaks back into content.

Store markup, not styling

Markdown and MDX store structure: this is a heading, this is a list, this is a link. HTML pasted from a word processor stores fonts, colours and inline widths, which is the thing you were trying to avoid.

Components are the escape hatch

When a post genuinely needs a callout or an embed, expose it as a named component the writer can use — <Callout> — rather than letting them hand-write a styled div. The renderer decides what a callout looks like. The writer decides where one goes.