Two more things...

One more bit of feedback...

In my opinion, the 'Submit' button should be visible/accessible while you're still in this top part of the page with the text editor box. Either between the 'Body' and 'Preview' sections, or just below the Preview.

I don't like having to scroll all the way to the bottom of the page just to submit a post. And it feels really misplaced and inconvenient for it to be below even the attachments section (which you won't be using or need to see a vast majority of the time).

Alternatively, what if the Attachments section was collapsed by default, so it isn't taking up so much space on the page? Just click it to expand and show the whole thing for those times where you actually want to attach things.

Also, if the Preview panel could auto-scroll to the bottom of your post (where you are likely adding text), or even pick out where you are adding text and move it to show that section specifically, it would be awesome.