How to get user's comments in the workflow activity by InfoEngine task?

If you are open to use Java APIs, you may want to try something like below to get Routing History,

wt.fc.collections.WTArrayList auditCol = (wt.fc.collections.WTArrayList) wt.workflow.engine.WfEngineHelper.service.getVotingEvents((wt.workflow.engine.WfProcess)self.getObject(), null, null, null);
System.out.println("***Transition Expression: Audit = " + auditCol.toString());
java.util.Iterator auditEvents = auditCol.persistableIterator();
comments = "";
while( auditEvents.hasNext())
{
wt.workflow.engine.WfVotingEventAudit audit = (wt.workflow.engine.WfVotingEventAudit)auditEvents.next();
System.out.println("***Transition Expression: User vote = " + audit.getEventList());
System.out.println("***Transition Expression: User comment = " + audit.getUserComment());
comments += audit.getUserComment();
System.out.println("***Transition Expression: Complete Time = " + audit.getPersistInfo().getCreateStamp());
}
System.out.println("comments = " + comments);