title: Why does the polymer property binding need a tag in my template?
body: <p>I am trying to understand how Polymer renders properties in the template of a custom element. I'm seeing some behavior that I can't explain, where some properties are being rendered in one case (when surrounded by tags), but not in another (when tags are not present in the template). To demonstrate the behavior I wrote this Plunker:</p>
  
  <p><a href="http://plnkr.co/WHYZKrjMMTMckw4X6p4Q" rel="nofollow">http://plnkr.co/WHYZKrjMMTMckw4X6p4Q</a></p>
  
  <p>Basically what I did is that I wrote the following custom element:</p>
  
  <pre><code>&lt;link rel="import" href="http://www.polymer-project.org/1.0/samples/components/polymer/polymer.html"&gt;
  &lt;dom-module id="characters-label"&gt;
    &lt;style&gt;
    &lt;/style&gt;
    &lt;template&gt;
      This has {{ncharacters}} characters!
    &lt;/template&gt;
  &lt;/dom-module&gt;
  &lt;script&gt;
    Polymer({
      is: "characters-label",
      properties: {
        ncharacters: {
          type: String,
          value: '6'
        }
      }
    });
  &lt;/script&gt;
  </code></pre>
  
  <p>and I use it like this in an index.html file:</p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html&gt;
  
    &lt;head&gt;
      &lt;script data-require="polymer@1.0.0" data-semver="1.0.0" src="http://www.polymer-project.org/1.0/samples/components/webcomponentsjs/webcomponents-lite.js"&gt;&lt;/script&gt;
      &lt;script data-require="polymer@1.0.0" data-semver="1.0.0" src="http://www.polymer-project.org/1.0/samples/components/polymer/polymer.html"&gt;&lt;/script&gt;
      &lt;link rel="import" href="characters-label.html" /&gt;
    &lt;/head&gt;
  
    &lt;body&gt;
      &lt;p&gt;This is before my label&lt;/p&gt;
      &lt;div&gt;
        &lt;characters-label&gt;&lt;/characters-label&gt;
      &lt;/div&gt;
      &lt;p&gt;This is after my label&lt;/p&gt;
    &lt;/body&gt;
  
  &lt;/html&gt;
  </code></pre>
  
  <p>The result doesn't render the value '6' in the HTML, but instead I get the literal contents of the template:</p>
  
  <p>This is before my label<br>
  This has {{ncharacters}} characters!<br>
  This is after my label  </p>
  
  <p>However, if I change my custom element's template to:</p>
  
  <pre><code>&lt;template&gt;
    This has &lt;b&gt;{{ncharacters}}&lt;/b&gt; characters!
  &lt;/template&gt;
  </code></pre>
  
  <p>Then the result is as expected:</p>
  
  <p>This is before my label<br>
  This has <strong>6</strong> characters!<br>
  This is after my label  </p>
  
  <p>Is this normal behavior?</p>