additional clarification comment

serviceinterface/ServiceInterfaceStream.h

@@ -7,6 +7,9 @@
 
 // Unfortunately, there must be a forward declaration of the log front end
 // (MUST be defined in main), to let the system know where to write to.
+// The ServiceInterfaceStream instances (declared below and instantiated in main)
+// can be passed to these front ends by passing their underlying buffers
+// with .rdbuf()
 namespace sif {
 extern std::ostream debug;
 extern std::ostream info;