/**
* Replace existing greeting tokens in message/subject.
*
+ * This function operates by reference, modifying the first parameter. Other
+ * methods for token replacement in this class return the modified string.
+ * This leads to inconsistency in how these methods must be applied.
+ *
+ * @TODO Remove that inconsistency in usage.
+ *
+ * ::replaceContactTokens() may need to be called after this method, to
+ * replace tokens supplied from this method.
+ *
* @param string $tokenString
* @param array $contactDetails
* @param int $contactId