If you want to write simple documents using a plain text editor but still want to add basic text formatting, you can use Markdown: John Gruber's formatting system, with which you use short and easy-to-remember codes to mark up your text. Lots of websites and blogs are already using Markdown, so you can enter plain text and still have it formatted the way you want.
With my Javascript markdownID), you can select existing text or import a Markdown file, and it will be converted into properly styled text for InDesign.
The script supports lots of the standard functions from the original Markdown, and so you can use the Markdown reference for the basic set of commands. Unfortunately, there are also some functions that InDesign cannot easily emulate.