I think the main argument against power-levelers is that the majority of them aren\'t interested in roleplaying at all, and thus use OOC talk (with stats, numbers, etc.) continuously in the chat, usually with no desire to use parentheses or brackets of any kind. Playing a character who enjoys killing or hunting does not make the character a power-leveler by itself. It\'s the missing roleplay aspect that does it - who is doing the killing: the earthman, Johny, or his Yliakuun Enkidukai, Anukoruhn (random example)? Characters have histories, reasons for actions, reasons for killing. If he\'s here just to kill pixels on the screen, Johny doesn\'t belong in PlaneShift and will be better accepted by the communities of other, less strict games. If his character however is a bloodthirsty hunter who kills to know that he is alive, Johny and his Enki will be embraced with open arms by the roleplay community. But there is a clear difference.
If you do not roleplay, if your character is not separate from your own persona enough to permit roleplay, something must be done - either finding a game better suited to the power-leveler\'s needs, or trying to build a better character with words instead of stats.