We'll create fresh WordPress site with CodeMirror for Post Editor installed. You have 20 minutes to test the plugin after that site we'll be deleted.
This plugin adds an editor button that will let you use the great CodeMirror editor to edit the HTML code of your posts.
This editor supports code coloring and automatic tag closing on a big editor that will let you write beautiful code on your WordPress posts.
Probably the best choice if you need to use complex HTML on your posts, or just enjoy writing in plain HTML.