In Sculpt Mode, users can hold Ctrl to invert the effect of the current tool. However, both the tool settings + and - buttons, as well as the color of the brush cursor, don't update to reflect that you've inverted the effect.
Both of these should update their state when the user holds Ctrl.
The same is true for the selection tools and their modes.
When holding Shift or Ctrl to add or remove, the state of these buttons should update to reflect that.