There's another thing I discovered with touchpads: the tap-to-click, which I turned off wherever I could in order to avoid confusion about sudden, unanticipated click events. Once again, this had to be done in every desktop environment I evaluated in a range of different dialogues. Fortunately, the GNOME developers hadn't decided that tap-to-click was purely beneficial and not to be removed from the user experience, so for this I give them credit.
As far as selection markers are concerned, they should really appear as a pop-up that is offset (horizontally, most likely) from the icon/name combination in something like Dolphin, so as to avoid trespassing on the icon in a potentially non-obvious fashion for people who have to squint to see such things or who don't have normal colour vision.