The QDU has recently updated its rules. The rules are available here, and it is recommended that all debaters and coordinators read and fully understand those rules. The most significant update in this revision is to Section 8, and rules 8.4 and 8.5, which now read (revisions are underlined):
8.4 Teams that do not have three debaters present for a debate will be deemed to have forfeited that debate. Debates may proceed if the teams wish to proceed with fewer than three debaters on a team, but the result will be disregarded and the team with fewer than three debaters will be deemed to have forfeited the debate. For the sake of clarity, the QDU will allow debates to proceed with fewer than three debaters so that the preparation of the debaters in attendance get the opportunity to speak to the topic they have prepared and receive feedback on their debating.
8.5 Any team debating a team in breach of rules 8.3 or 8.4 will be accredited a win.