add comment about storing initial top hash

core/direct-rpc-server/src/rpc_responder.rs

@@ -108,6 +108,11 @@ where
 		self.encode_and_send_subscription_update(connection_token, &sub)?;
 
 		if do_watch {
+			// We just store back the initial response, which is the top hash.
+			// This was implemented before we added the `RpcSubscriptionUpdate`
+			// and should probably be refactored in the future.
+			//
+			// But for now this is fine, as we only use it to track ongoing connections.
 			self.connection_registry.store(hash, connection_token, rpc_response);
 		}