What problem does this address?

Currently, copy/pasting of Markdown does not format in the block editor or on the front end.

Opinion: Markdown should be a first-class writing interface in WordPress.

Enhancement

Improve block editor and front-end Markdown UX

• copy/paste Markdown into Gutenberg
• Headings, paragraphs... lists, etc.. transformed

@t-hamano suggested to open the issue for discussion.