We discovered today that a lot of people mailing in tickets aren't getting emailed about updates to them. After some testing we found out that the author of the email isn't getting added to the subscribers-list, and therefore doesn't get any updates.
Our setup is a small fetchmail-procmail-chain that checks for new emails on an account and sends them to the mail_handler.php-script included in the phabricator distribution. Our phabricator-install is relatively up to date, and the mail_handler-script doesn't seem to have been updated since.