Some things which I noticed (on Chromium 62, Linux):
-
While the composer opens, the scroll bar of the edit area flickers frantically. Happens when unhiding the composer as well.
-
When you hide the composer window, the hide button turns into an X, which apparently cancels the message entirely. However, it shows no warning (like the cancel button does) and its tool tip still says “hide or show the composer panel”. I’m afraid that may sting a few people with in-progress posts.
-
The line width around the edit area is inconsistent, being two pixels in some places and one pixel in other places.