The computed value of a property is often incorrect. That is if a computed value is dependent on another property, that other property is ignored. This can be tested using the inherit keyword.
Public testcase: http://the-dees.webs.com/iepp1/22-computed-value.html
This bug was previously reported a few times, see
ID#344787 (Inherited margin with inherit keyword: the computed value's parent should be inherited),
ID#429559 (TH element does not inherit text-align),
ID#469093 ('border-color' of ascendant isn't inherited (using 'border-color:inherit') when that element has a 'color' value defined).
The problem is not local to the properties mention but global, i.e. it applies to any property.