Tested on macOS 10.13
Usually I type my words into vi, but today I'm composing this page in TextEdit.app.
TextEdit.app is pre-installed on every Mac and supports plain text. To start using it for plain text files, set these defaults.
Note: You can also adjust the default font and size by clicking on Change beside Plain text font.
You can always adjust the font size in the current window with ⌘+ and ⌘-.
Optionally, go to Preferences > Open and Save. Check When Opening a File to Display HTML files as HTML code instead of formatted text.
Now you can close the TextEdit window and open a new one in plain text.
You can write some prose in TextEdit, but editing long texts, especially across multiple files, is inefficient. Frankly, I switched to Vim to edit this page as soon as the first draft was complete.
Plain text is awesome!