For this kind of field:
I’d really like to be able to post images directly from my clipboard.
I heavily rely on pasting images like this in many places on the Internet as all the screenshots I take with various tools (even Windows built-in tool) go to my clipboard. 
I also would like to be able to easily use markdown formatting. There’s no toolbar and shortcuts don’t work. Plus, there’s no result preview as well.
This feature is excellent and will be useful in many ways, but when I use it, I miss some of the regular composer features (depends on what’s asked in the fields though; the template I use would benefit from them).