Anyways, I went to the trouble of unblocking it. This involved going to OSX's settings dialog and finding the Security & Privacy window to unblock.
The text rendering is awful. It's blurry and smudged on my non-retina display due to not using subpixel smoothing. Here's a screenshot comparing Atom (top) to Mark Text (bottom): https://imgur.com/UEJbsl4
Highlighting and pasting text is totally unpredictable. Try pasting in 10 * characters and you'll see that it's almost impossible. How are you supposed to do this? Sometimes it replaces * with \*, sometimes not. And sometimes it replaces it with - ??
I tried to copy paste a few paragraphs of text a few times, and once it turned into this strange highlighted text that when I started a new paragraph, deleted all of my newlines. What's going on?
This editor does not seem ready yet.