I enjoy and highly recommend Juval Lowy\'s - C# Coding Standard. Juval explicitly avoids rationale for each directive in order to keep the standard tight (see the preface). Howe
Regarding 1.13 (Avoid fully qualified type names. Use the "using" statement instead):
It may be a bit more than readability. If you have too many usings at the beginning of the file, you have a class that is coupled with classes from too many namespaces.
The class is screaming out for refactoring. Using usings instead of fully-qualified class names lets you identify such tightly-coupled classes more easily.