Pere, thank you for your prompt response. I tried playing with the display percentage, and that changed the size of the icons, but did not affect the difference in size and spacing of the particular aspects that are distorted.
I'm including two more screenshots to show that it is just these two areas (Layer List and Line Parameters) that are smaller. On the second image, you can see where I've moved the Line Parameters group to another icon row, and it makes the new icon row skinnier than the normal rows above. Strange.