+/**
+ * Resolve an ambiguous profile nickname reference, checking in following order:
+ * - profiles that $sender subscribes to
+ * - profiles that subscribe to $sender
+ * - local user profiles
+ *
+ * WARNING: does not validate or normalize $nickname -- MUST BE PRE-VALIDATED
+ * OR THERE MAY BE A RISK OF SQL INJECTION ATTACKS. THIS FUNCTION DOES NOT
+ * ESCAPE SQL.
+ *
+ * @fixme validate input
+ * @fixme escape SQL
+ * @fixme fix or remove mystery third parameter
+ * @fixme is $sender a User or Profile?
+ *
+ * @param <type> $sender the user or profile in whose context we're looking
+ * @param string $nickname validated nickname of
+ * @param <type> $dt unused mystery parameter; in Notice reply-to handling a timestamp is passed.
+ *
+ * @return Profile or null
+ */