[Orion]

I think it depends on the setting. If you have a world where character killing (I refuse to call it player killing, because it makes it sound personal, and I have no idea why it was called that in the first place,) is not common, then it makes sense to restrict CK.

I've found in RP MUDs that have permadeath and unrestricted killing, that it actually harms plots, because no one's willing to oppose other characters in case their character is killed as a result.

Some kind of system where experience points are reimbursed, to be spent on your next character, I think softens the blow to the player.

Is a player just killing another character because they as a player don't want to lose thier character and are powergaming, or does the character doing the killing actually have motivations behind taking such an action? These are things I would look at as a staff member on my MUD.

I prefer that CK be a last resort really. There are other things you can do to mess up the plans of another character besides killing them, which can be much more fun. There are many situations in which you could choose an alternative course of action, it's just that players can be lazy when it comes to thinking up stuff like that, or the game makes it difficult for them to do so.