Strongly disagree—it should be a standard feature, along *with* TinyMCE, because then it would force them to take it seriously and work on implementing it in a way that encourages mainstream adoption.

The problem with WP's markdown implementation, as it stands, is that it doesn't support key commands, and assumes people want a bare editor. It should, and they don't. I get the serious impression that WP doesn't put much effort, if any, into the code editor side of things—assuming that all people who understand HTML want is a plain text editor.

To be fair, a LOT of platforms that implement MD get this wrong.