In configuration file of Zabbix agent (have not checked with Zabbix agent 2), if ServerActive field has several values and one or more of them are duplicates of the first, than agent does not start with "error parsing the ServerActive parameter: address x.x.x.x specified more than once" error, if the first value is unique and duplicates exist only for other values, then agent starts without any errors.

There should be consistency in validation, and either agent should ignore duplicates or fail with errors on any duplicate values not just duplicates of the first value.