more details on launch_sibling in comments

src/own.cpp

@@ -80,13 +80,19 @@ void zmq::own_t::launch_child (own_t *object_)
 
 void zmq::own_t::launch_sibling (own_t *object_)
 {
+    //  At this point it is important that object is plugged in before its
+    //  owner has a chance to terminate it. Thus, 'plug' command is sent before
+    //  the 'own' command. Given that the signaler preserves ordering of
+    //  commands, 'term' command from the owner cannot make it to the object
+    //  before the already written 'plug' command.
+
     //  Specify the owner of the object.
     object_->set_owner (owner);
 
     //  Plug the object into its I/O thread.
     send_plug (object_);
 
-    //  Take ownership of the object.
+    //  Make parent own the object.
     send_own (owner, object_);
 }