I had the review page open to fill half my monitor (how I normally browse the Q&A). I wanted to vote to reopen, but I couldn't see the reopen action even when I scrolled over.
Unfortunately, it looks my gif didn't quite record correctly, but if you look closely you'll see that even when scrolled all the way to the right, only the "Leave Closed" and "Edit and Reopen" buttons are visible.
This was on Code Review. I'm on Chrome Version 64.0.3282.186 (Official Build) (64-bit).
My resolution is 1920 x 1080, and the window took up one half of the screen originally (I shrank it more for the gif, but the behavior was the same).