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-continue>
    <revisions rvcontinue="492" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1" ns="0" title="Main Page">
        <revisions>
          <rev user="Soutyou" timestamp="2015-05-25T22:13:21Z" comment="[[JUNKWIKI]]への転送ページ" />
          <rev user="Soutyou" timestamp="2015-04-15T18:48:22Z" comment="[[Special:Contributions/Soutyou|Soutyou]] ([[User talk:Soutyou|トーク]]) による版 609 を取り消し" />
          <rev user="Soutyou" timestamp="2015-04-15T18:47:23Z" comment="内容を「#REDIRECT [[メインページ]]」で置換" />
          <rev user="Soutyou" timestamp="2015-04-15T18:47:05Z" comment="[[メインページ]]への転送ページ" />
          <rev user="Soutyou" timestamp="2015-04-15T18:45:16Z" comment="" />
        </revisions>
      </page>
    </pages>
  </query>
</api>