Drafts is focused on plain text. It does not support rich, word processor style text, and that is not likely to change. That is largely to allow the level of integration with so many different services and outputs. Plain text is the least common denominator, if you will. Rich-text introduces a lot of complexity and inconsistencies that would not fit well with the many different integrations available in Drafts.
One approach worth looking at is on Mac OS is to use Marked 2 to get a live display of your text as you edit. This is the approach I use, as it lets you write in Markdown and get all the advantages of document portability etc., but still have a WYSIWYG view of your content.
Even better, Marked has very powerful styling and exporting features, so you have huge flexibility in your document creation and publishing tool chain. I frequently take meeting minutes in Drafts, and publish in both HTML and PDF format (using a Keyboard Maestro script.)
Marked offers a free trial, so it’s worth taking a look. Drafts + Marked gives you a very powerful and flexible tool chain.