Could the section 6.8. Check Boxes benefit from more strict guidelines on negating labels I.e. discouraging labels that effectively says "Check here to make this object invisible". A more wise implication would be "Check here to make this object visible" whether it's a desirable action or not.

For a quick example, not saying they're wrong though, Gedit has a checkbox setting labelled "Do not split words over two lines". To avoid any confusion, a better label would be "Allow words to be split over two lines" obviously with the effect having been inverted.