While it is true that the labels for some diagnostic options get cut off, the layout follows the standard spacing for elements in the Preferences window. The 'Reset' button is also intentionally smaller than a regular button, using the 'miniButton' style, to allow the options to be packed vertically into the window as efficiently as possible.
Given that the diagnostic preferences are not intended for general use by customers, we will not spend time polishing the aesthetics of it at the current time.