Better comments and parameter names.

module.js

@@ -9,18 +9,21 @@ import { Observable } from "zen-observable/esm.js";
 // Observable.apply methods with an implementation that calls
 // Reflect.construct instead, when available.
 
-Observable.call = function (obs, sub) {
-  return construct(this, obs, sub);
+Observable.call = function (instance, subscriber) {
+  // Since Observable.call is a static method, 'this' will typically be the
+  // Observable constructor function, though it could be a subclass of the
+  // Observable constructor, which is why we don't just hard-code it here.
+  return construct(this, instance, subscriber);
 };
 
-Observable.apply = function (obs, args) {
-  return construct(this, obs, args[0]);
+Observable.apply = function (instance, args) {
+  return construct(this, instance, args[0]);
 };
 
-function construct(Super, self, subscriber) {
+function construct(Super, instance, subscriber) {
   return typeof Reflect === 'object'
-    ? Reflect.construct(Super, [subscriber], self.constructor)
-    : Function.prototype.call.call(Super, self, subscriber) || self;
+    ? Reflect.construct(Super, [subscriber], instance.constructor)
+    : Function.prototype.call.call(Super, instance, subscriber) || instance;
 }
 
 export { Observable }