Make %username contain name of active user, instead of node author.

Relevant code is below. I agree that this should be changed, although it is up to Gabor whether it can still get into D6.

// system.module

  $recipient = $context['recipient'];

  if (isset($node)) {
    if (!isset($account)) {
      $account = user_load(array('uid' => $node->uid));
    }
    if ($recipient == '%author') {
      $recipient = $account->mail;
    }
  }

  if (!isset($account)) {
    $account = $user;

  }
  $language = user_preferred_language($account);
  $params = array('account' => $account, 'object' => $object, 'context' => $context);
  if (isset($node)) {
    $params['node'] = $node;
  }

  if (drupal_mail('system', 'action_send_email', $recipient, $language, $params)) {
    watchdog('action', 'Sent email to %recipient', array('%recipient' => $recipient));
  }
  else {
    watchdog('error', 'Unable to send email to %recipient', array('%recipient' => $recipient));
  }
}

/**
 * Implementation of hook_mail().
 */
function system_mail($key, &$message, $params) {
  $account = $params['account'];
  $context = $params['context'];
  $variables = array(
    '%site_name' => variable_get('site_name', 'Drupal'),
    '%username' => $account->name,
  );

I propose to change this to: (no patch unless this goes through)

// system.module

  $recipient = $context['recipient'];

  if (isset($node)) {
    $author = user_load(array('uid' => $node->uid));
    if ($recipient == '%author') {
      $recipient = $author->mail;
    }
  }

  if (!isset($account)) {
    $account = $user;
  }

  $language = user_preferred_language($account);
  $params = array('account' => $account, 'object' => $object, 'context' => $context);
  if (isset($node)) {
    $params['node'] = $node;
  }

  if (drupal_mail('system', 'action_send_email', $recipient, $language, $params)) {
    watchdog('action', 'Sent email to %recipient', array('%recipient' => $recipient));
  }
  else {
    watchdog('error', 'Unable to send email to %recipient', array('%recipient' => $recipient));
  }
}

/**
 * Implementation of hook_mail().
 */
function system_mail($key, &$message, $params) {
  $account = $params['account'];
  $context = $params['context'];
  $variables = array(
    '%site_name' => variable_get('site_name', 'Drupal'),
    '%username' => $account->name,
  );

system_mail does not use $account anywhere else, so changing $account to be the user rather than the author does not make any other difference. I propose that in D7, both $author and $user variables become available; in DRUPAL-6 this would require string changes.

Enclosed is an untested patch with the changes proposed by Arancaytar.

Moving this to the D7 queue.

This patch still applies, but as I stated earlier, this should be improved since in D7 we can still change strings.

Subscribing.

An option would also be to keep a token for the node author, in case someone wants to use that string. Something like this in system_mail:

  $variables = array(
    '%site_name' => variable_get('site_name', 'Drupal'),
    '%authorname' => $author->name,
    '%username' => $user->name,
  );

Seems relevant still

This has been fixed in #113614: Add centralized token/placeholder substitution to core: Add centralized token/placeholder substitution to core.

Marking this as duplicate.