Would a human tail be prehensile? Would we use it to maintain balance? In those cases a sleeve might be quite uncomfortable.
If we used our tails to communicate, like dogs do, would we be able to "read" a clothed tail? I think so.
@jkb Apes (and humans) are more closely related to old world monkeys or circopithecidae which have non-prehensile tails. New world monkeys or atelidae have prehensile tails and are evolutionarily more distantly related to humans. So I would think humans would have non-prehensile tails more similar to macaques and baboons rather than the prehensile tales of spider monkeys. But if we did have tails they would interfere with our upright bipedal gait and big butts.