I guess it would be possible, but what we were aiming for was something a bit more organic. We don’t really want to make another markdown editor — there are already many of those.
Many apps using markdown are using it because they are web based, and don’t have much choice. Support for WYSIWYG text editing on the web is pretty prosaic. It’s much easier just to use plain text, and convert that to something that looks nice when you save.
We are trying to be more ambitious. We want nicely styled text, but also the convenience of simple shortcuts that people are used to, hence the markdown. There are still a few rough edges, but we are improving this all the time.
If you don’t want to use markdown, there should be very few moments when it gets in the way. There are a few at the moment, but we have some fixes coming that will help with those too.