Re #6807. Make comments more general.

The previous comments don't belong in this general class as they were
talking about very specific SNS/ADARA/SMS things.

Code/Mantid/Framework/LiveData/src/StartLiveData.cpp

@@ -194,14 +194,12 @@ namespace LiveData
     // Adjust the StartTime if you are starting from run/now.
     if (FromNow)
       this->setPropertyValue("StartTime", "1990-01-01T00:00:00");
-      // Use the epoch value for the start time.  It will get converted to 0 when passed
-      // to SMSD in the ClientHello packet.  See the description of the ClientHello packet
-      // in the ADARA network protocol docs.
+      // Use the epoch value for the start time, as documented in ILiveListener::start.
     else if (FromStartOfRun)
       // At this point, we don't know when the start of the run was.  Set the requested time
-      // to 1 second past the epoch (which will get turned into 1 when passed to SMSD in
-      // the ClientHello packet) which will cause the SMS to replay all the historical data
-      // it has.  We'll filter out unnecessary packets down in the live listener
+      // to 1 second past the epoch, which is sure to be before that. We're then relying
+      // on the concrete live listener to never give data from before the current run.
+      // So far, any that give historical data behave like this but there's no way to enforce it.
       this->setPropertyValue("StartTime", "1990-01-01T00:00:01");
     else
     {