It depends on the offense, if you go around harassing people or just saying things that aren't funny like your mom in randomthreads, you deserve to not be able to post for a long while.
Most people don't really worry about their levels, they just don't deposit so say taking away 10xp from someone who has been here 6 years and is level 3 wouldn't be punishment at all but taking away 10xp from Pimp would be the ultimate "FUCK YOU".
It all depends, which makes it controversial and difficult.
I've only been banned once, and I deserved it, it was more or less for me being a tard, I didn't break anyrules other than short posting and being a dumbfuck. it was a 20 hour ban.
It was a thread about gas prices, the OP asked why are they so i high and i was quick to respond "because you touch yourself at night"