When clicking the "back" button to hide the keyboard, the toolbar doesn't show up again even when you click the text box. Only when you start typing does it reappear. (Yes, very minor, but could be annoying.)
Image upload. THANK YOU SO MUCH FOR THIS! Really amazing. But at first, it confused me, because after selecting an image to upload, nothing seemed to happen. The image only appeared in the post after about 10 seconds.
Could this please be changed so that there's a progress bar, or... at least some kind of visual indicator that the image is indeed uploading?
Two minor things with code formatting: a.) It doesn't know how to do inline formatting (it makes a 4-space-indented block even when only a single word is selected), b.) It inserts two blank lines above and below a code block when only one is necessary.
Overall, though, it looks amazing. Great job!