When entering string commentary in a DBR cell the left arrow key doesn’t work. (right arrow key works fine). So the only way to go back a few keystrokes to correct a typo is to use the mouse.
The left arrow key when WITHIN the text in a cell still has the Shift+Tab function of cell left. Right arrow has character right function as expected with within text in cell and when whole cell same as Tab of next cell to right. So I would class this as a bug, the behaviour of left & right arrow when within text should be consistent.