Switch from MAY to SHOULD for language expression.

Call out underlying defaults of `Undefined` for language and `auto` for base direction when no metadata is provided.

Co-authored-by: Ted Thibodeau Jr <[email protected]>

index.html

@@ -5721,14 +5721,18 @@ <h3>Language and Base Direction</h3>
         <h3>Providing Default Language and Direction</h3>
 
         <p>
-A default language and direction MAY be provided for the entire credential.
-However, doing so introduces a higher demand on context creators and 
-downstream processors. Consequently, using default language and
-direction is expected to be be limited to scenarios where JSON-LD expansion-based
-transformation can be assured. See the
-<a date-cite="JSON-LD#string-internationalization">String
-Internationalization</a> section of the [[JSON-LD]] specification for more
-information.
+The language and base direction of each natural language string property SHOULD
+be provided, either via the language value structure for each property or via a
+default language and base direction for the entire credential. Using the
+language value structure is preferred, because document defaults can result in
+a requirement that downstream processors perform JSON-LD expansion-based
+transformation which is otherwise optional. See the <a
+data-cite="JSON-LD#string-internationalization">String Internationalization</a>
+section of the [[JSON-LD]] specification for more information. Natural language
+string values that do not have a language associated with them SHOULD be
+treated as if the language value is `Undefined` (language tag "`und`"). Natural
+language string values that do not have a base direction associated with them
+SHOULD be treated as if the direction value is "`auto`".
         </p>
       </section>