Since DyCham said it was possible in S3, I had to figure out how.
In the QuickReference panel, select the dropdown that defaults to 'Editor' and choose the 'Comments/Footnotes' option.
When you do the Comments are displayed below the Editor pane in the QuickReference panel.
But just to the right of that dropdown, a symbol representing the option to change the split appears. Click that symbol representing a vertical split and you'll have the QuickReference panel configuration you were looking for (I think).

- QuickReference Panel with Vertical Split
- Screenshot 2017-11-24 09.36.46.png (108.13 KiB) Viewed 777 times