When activating the 'single click' feature, selecting by CTRL or SHIFT doesn't work properly.
It isn't possible to select by pressing one of these keys down and clicking an item (like it does without 'single click'). After having pressed one of these keys, the mouse constantly hilights the respective items it is over. Now pressing CTRL or SHIFT will finally select the item, but the mouse doesn't stop hilighting other items when moved which is confusing and annoying.
Selection with CTRL and SHIFT should work identically with or without 'single click' enabled.