Secondly, in a question that may be related, why do so many people feel the game only starts at really high levels? It's to the extent that for some extreme holders of this view pk at lower level seems to be held in contempt, like kicking a guy in a delicate place during a boxing match.

At lower levels:
You don't have many class skill/spells
You can't visit many tough areas
You can't gather great artifacts
You can't play a significant role in cabal wars

So that's why many feel that the game starts at high levels.
After all, fighting for something at level 10 makes little sence (except for fun, but it only works once) when you can spend 1 hour ranking and do the same things with much less efforts at level 15.

Level sitting at low levels bothers players because a competent levelsitter has significant advantages over you.
He usually has better armor than newcomers (Cabdru was an exception), his skill percentage is higher, he usually have a key ability for this level while you don't yet. (assassins at 36, warriors at 15 where they get bash, shamans with sanc and summon and so on).
So, basically, in most cases you have either: avoid that level sitter and rank through or gather a gang to stand against him. (But in the second case he simply quits and logins a week later to slay new people).
That's why people thinks that levelsitting is cheap (and it really is).