In previous discussions, it usually turned out that "allowed" meant that it was not covered in the tournament rules at all. At best, there was an ad hoc ruling by a judge, who, understandably, made a snap decision (which may or may not have been wrong) to keep the game flowing. After all, games are definitely not the place for lengthy discussions about the rules. And common misconceptions are not that likely to be challenged at tournaments in the first place, precisely because they are common.