New Twiddle

application.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Content Editable',
  myText: 'Here is some text now.'
});

application.template.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{contenteditable-component model=myText}}
<br>
<br>
{{myText}}
<br>
<br>
{{input value=myText}}
<br>
<br>

contenteditable-component.component.js

import Ember from 'ember';

export default Ember.Component.extend({
  tagName: 'span',
  attributeBindings: ['contenteditable'],
  contenteditable: true,
  keyUp(e) {
    this.set('model', this.get('element').textContent);
  }
});

contenteditable-component.template.hbs

{{model}}

twiddle.json

{
  "version": "0.6.4",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.4.1/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.4.0/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.4.1/ember-template-compiler.js"
  }
}