#Amethyst is the only one I know of that renders markdown in kind 1 notes. Markdown in kind 1 is NOT expected in NIP-10. They are meant to be simple, plaintext notes.

Clients are not even necessarily expected to render anything other than text in kind 1 notes. Most have determined to render URLs that point to images or videos as the image or video itself, rather than requiring the user to copy/paste the URL to open it in a separate application, but even this is not technically required by the definition of what a kind 1 note is. Client devs just recognize that it is better UX.

By contrast, long-form notes (kind 30023) are defined as containing markdown syntax, rather than plaintext. Any client supporting long-form notes, should render the markdown syntax accordingly.