Update documentation for metadata strings.
@@ -1365,9 +1365,9 @@ identifier/value pairs like in the following example:
As can be seen in the example, metadata identifiers are always followed by
an equals sign and the value assigned to them. The assigned values can be
-strings, integers, or one of the boolean values true or false. Note that
-identifier/value pairs defined in the metadata section can not be used in
-the condition section, their only purpose is to store additional information
+strings (valid UTF8 only), integers, or one of the boolean values true or false.
+Note that identifier/value pairs defined in the metadata section can not be used
+in the condition section, their only purpose is to store additional information
about the rule.
.. _using-modules:
