Register nodes seen in a view as not "new"
The New or Updated mark is generated by a simple theme function (theme_mark) which can be overriden. Normally you would do that in your template.php but since this theme function is used in the admin theme, that's not gonna work.

A workaround for this is to add your own theme function to a custom module, like this:

/**
 * Implements hook_mark().
 */
function yourmodule_mark($variables) {
  // Always return an empty string.
  return '';
}


Now, we need to add this function to the theme registry like this:

/**
 * Implements hook_theme_registry_alter().
 */
function yourmodule_theme_registry_alter(&amp;$theme_registry) {
  // Check if the default theme function of mark exists
  // and override it with our own theme function.
  if (isset($theme_registry['mark']['function']) {
    $theme_registry['mark']['function'] = 'yourmodule_mark';
  }
}


Clear your cache and your done.

You'll find the original theme function here in the Drupal docs.

Note that this code will permanently override the output of this function where ever it is used.