+ /**
+ * Check whether the given nickname is potentially usable, or if it's
+ * excluded by any blacklists on this system.
+ *
+ * WARNING: INPUT IS NOT VALIDATED OR NORMALIZED. NON-NORMALIZED INPUT
+ * OR INVALID INPUT MAY LEAD TO FALSE RESULTS.
+ *
+ * @param string $nickname
+ * @return boolean true if clear, false if blacklisted
+ */