I think you express the precise reason why I prefer markup formats like Markdown, ReDoc, and LaTeX. I get to write markup which completely eliminates the need to click around menus and buttons or do app-specific keyboard shortcuts for formatting.

Rich wysiwyg editors also seems to have issues where the visible editing and internal formatting state breaks or behaves in weird ways. Like when you insert links and it automatically formats it as a link in some cases, and not in others.

Edit: Personally I always though the split view was okay as long as the compile times weren't too bad. Having a markup editor and then a view of the result is what I do for coding, so why not when writing stuff as well.