WordPress Admin isn't a great markdown writer
I spent an afternoon trying to make WordPress a markdown editor. wp-env, a small mu-plugin that unhooks the admin chrome, another mu-plugin that swaps TinyMCE for EasyMDE, Parsedown converting on save into post_content, with the raw markdown kept in post meta so editing round-trips. It works; task lists render, the toolbar behaves, edits come back as markdown.
But it's still wp-admin. The textarea sits inside the post edit screen, surrounded by sidebars and metaboxes and the admin bar, and none of that goes away just because the editor itself is now markdown. The thing I'm doing is still configuring a post in an admin panel, not writing, and polishing the EasyMDE chrome made it look nicer but didn't change that.
Maybe I should have just enabled the Micropub plugin and IndieAuth for the auth side, and post from iA Writer. iA Writer does the writing, WordPress does the storing and publishing, and I don't have to bend wp-admin into something it isn't.
