This just doesn't seem right to me. Murder should be a dramatic and exceptional event, something you do to a specially chosen victim because of rivalry, jealousy or spite, or out of self-defence because you really have to. Not just because it's a Friday afternoon and you feel like butchering the next ten noobs you run across. As such, I feel there should be a cost associated with murder.
My suggestion is to permanently drain an amount of black bile (say, 10) from a character whenever they commit murder, recoverable only through gluttony. This achieves the following:
- Murder becomes a dramatic event for the killer. It's no longer something you do willy-nilly; you only kill when you have a good reason to do so.
- Newbies get a soft form of permadeath protection. After all, killing random noobs isn't exactly profitable anymore.
- Rivals will still kill each other, given the chance. 10 BB is a cheap price to pay for the life of a well-developed character.
- Killers get to silence their guilty conscience by stuffing themselves full of cabbage cakes. Recovering after you commit murder isn't particularly hard, so long as you don't do it too often.
- Higher-bile characters must eat more than lower-bile ones to recover their maximum black bile. Such characters typically have easier access to high purity foods, so it evens out.
To avoid griefing by parking alts on someone's claim, killing a player on your claim should be free.
So why black bile?
- Black bile is already associated with criminal actions. Murder is about as criminal as it gets.
- Black bile is used as the "mental stat" in-game. A heavy conscience is obviously a mental condition.
Black bile also makes sense from the bits and pieces I've read on the internets. From wikipedia: "Melancholics* can [...] become preoccupied with the tragedy and cruelty in the world."(source). Death is a tragedy, and few things are more cruel than murdering another person. Thus it makes sense that anyone with excess black bile would be more inclined to commit murder on a regular basis**. Anyone with a shortage of black bile would be less likely to kill.
* The melancholic condition is associated with black bile. (source 1, source 2)
** This could be total BS to anyone with solid knowledge about philosophy and psychology and other (pseudo)sciency stuff - AKA not me. It's a video game. Anything that sounds like it could make sense goes, even if it's BS

TL;DR: Make murder permanently reduce black bile. Save the noobs!