Thanks. That's nice, but not exactly what I meant. By WYSIWYG editing I mean visual editing like Word or Google Docs, but saving Markdown; not typing Markdown and having a real-time preview separately.
Typora does this nicely; I type an asterisk, it looks like an asterisk, but when I close the asterisk, the text in between goes italic. The asterisks are hidden unless the cursor is within the italic part. I can double-click to select a word, press cmd-I, and the word goes italic (by adding the asterisks). Etc.
I realize this is a matter of personal preference but for me, using editors that are changing the text I write as I write it between code and markup is really annoying. I can buy using pure WYSIWYG (i.e. Word) or typing plaintext, but something is just off for me when the editor tries to do both. I prefer knowing whether what I'm looking at is the actual contents of the file or just a representation of them, but whatever floats your boat obviously. Since a terminal based editor will never be able to to what you require it to, unfortunately this means your selection for "optimized" editors is limited.