Need to filter items going to event storage in 800xA SV5.1 FP4
Yes it is possible to limit storage of each type of event. Go to service structure - > Event Storage Service -> service definition aspect -> Special configuration tab.
Navigate to AuditEvent_OperatorAction and change message count from 10000 to 1000.
It is not possible to filter the events that are stored in event storage but by above you can limit how many of 'junk' events will be stored. Rest storage will be available for 'good' events.