Yeah, that wouldn't be good to happen, but..

builds/4chan-X.user.js

@@ -820,6 +820,9 @@
     Callbacks.prototype.push = function(_arg) {
       var cb, name;
       name = _arg.name, cb = _arg.cb;
+      if (this[name]) {
+        this.rm(name);
+      }
       this[name] = cb;
       return this.keys.push(name);
     };

builds/crx/script.js

@@ -825,6 +825,9 @@
     Callbacks.prototype.push = function(_arg) {
       var cb, name;
       name = _arg.name, cb = _arg.cb;
+      if (this[name]) {
+        this.rm(name);
+      }
       this[name] = cb;
       return this.keys.push(name);
     };

src/General/lib/callbacks.class

@@ -3,6 +3,8 @@ class Callbacks
     @keys = []
 
   push: ({name, cb}) ->
+    @rm name if @[name]
+
     @[name] = cb
     @keys.push name