2.1.229 Part 1 Section 17.7.3, Toggle Properties
a. The standard states that if a toggle property is not explicitly set in direct formatting, the toggle property appears at multiple levels of the style hierarchy, and the value specified by the document defaults is true, the effective value is true.
In this case, Word determines that the effective value to be applied to the content shall be true if and only if its effective value is false for an even number of levels in the style hierarchy.
b. The standard states that if no value is encountered on a level of the style hierarchy, the property takes on its default value.
In Word, if no value is encountered on a level of the style hierarchy, the property takes on the value specified by the document defaults.