All web editors that I know of are based either on codemirror, used for instance by Ghost (before and after the ember rewrite) end even by the now popular programming IDE LightTable, either on Ace, which I believe is used by Discourse itself.
Mozilla Labs had a project called Bespin, then renamed SkyWriter, but it’s now dead and their page suggests to use Ace instead.
The markdown thing is somehow thin layer that you put on top of one of the two fat-ass editors above; there is an historic code called ShowDown, which is all over the web (it’s a dependancy for Ghost, for instance).
The folks at stackexchange improved it with things like XSS attack prevention, and published their code under the name pagedown.
TL;DR: No, no editor written from scratch in Ember as of now.