New Twiddle

application.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName:'Ember Twiddle',
  init() {
    setTimeout(()=>{
      this.set('value',
` 
<h2>Permito qualquer tag?</h2>

    entende pq Michael?
      `);
    }, 2000);
  }
});

application.template.hbs

Meu "input":
{{meu-input value=value}}

<h2>Valor livre de HTML </h2>
substitui as &lt;br/&gt; por \n e &amp;nbsp; por ' ':
<pre>{{value}}</pre>

meu-input.component.js

import Ember from 'ember';

export default Ember.Component.extend({
  classNames: ['meu-input'],
  attributeBindings: [ 'contentEditable' ],
  contentEditable: true,


  valueDidChange: Ember.observer('value', function() {
    this.element.innerHTML = Ember.Handlebars.Utils.escapeExpression(this.value)
    .replace(/\n/g, '<br/>')
    .replace(/ {2}/g, ' &nbsp;');
  }),
  
  input(event) {
    console.log(this.element.innerHTML);
    const value = this.element.innerHTML
    .replace(/&nbsp;/g, ' ')
    .replace(/<\/?div.*?>/g, '\n')
    .replace(/<br\s*\/?>/g, '\n');
    
    this.removeObserver('value', this, this.valueDidChange);
    this.set('value',  value);
    this.addObserver('value', this, this.valueDidChange);

  },
});

styles.app.css

body {
  margin: 12px 16px;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  font-size: 12pt;
}

.meu-input {
  border: 1px solid #999;
  border-radius: 6px;
  min-height: 1em;
  padding: 6px;
}

twiddle.json

{
  "version": "0.4.17",
  "EmberENV": {
    "FEATURES": {}
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.2.0/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.2.0/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.2.0/ember-template-compiler.js"
  }
}