Add a clarifying comment

src/systems/personal-space-bubble.js

@@ -74,6 +74,9 @@ AFRAME.registerSystem("personal-space-bubble", {
   tick() {
     if (!this.data.enabled) return;
 
+    // precondition for this stuff -- the bubbles and invaders need updated world matrices.
+    // right now this is satisfied because we update the world matrices in the character controller
+
     for (let i = 0; i < this.invaders.length; i++) {
       this.invaders[i].setInvading(false);
     }