<!DOCTYPE html>
<html>
<head>
  <title>mo movablelimits default value</title>
  <meta charset="utf-8"/>
</head>
<body>
  <math>
    <munder>
      <mo>∑</mo> <!-- This has movablelimits="true" in the operator dictionary -->
      <mi>x</mi>
    </munder>
    <munder>
      <mo>∫</mo> <!-- This has movablelimits="false" in the operator dictionary -->
      <mi>x</mi>
    </munder>
  </math>
</body>
</html>