You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query>
    <pages>
      <page pageid="234" ns="0" title="Main Page">
        <revisions>
          <rev user="Apm" timestamp="2015-09-29T16:04:35Z" comment="collapse multiredirect" />
          <rev user="Apm" timestamp="2015-02-13T17:37:14Z" comment="Redirected page to [[Mechadense&#039;s Atomically Precise Manufacturing Wiki]]" />
          <rev user="Apm" timestamp="2015-02-09T13:53:07Z" comment="Apm moved page [[Main Page]] to [[Mechadenses Atomically Precise Manufacturing Wiki]]: people need to know where they are" />
        </revisions>
      </page>
    </pages>
  </query>
</api>