The empty space does seem like one intended for the toolbar.
Bug 1817810 Comment 1 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
The empty space does seem like one intended for the toolbar. Curios on how this was configured: - whether it is being set to be scrollable or fixed in place - whether it is being placed at the top or at the bottom.