Even though I dont make the rules, i think I'll throw in my $.02. I say that when you decide to join a house, you agree that you should be open to attack from ANYONE in another house, regardless of level (though it is spineless to pk a lvl 1 while u are 100), remort level, or other reasons.
I think that when joining a house, there should be a popup disclaimer message, such as what you see when joining a tribes server, to warn the person joining of the risks of joining a house.
Also, I believe that it IS ok to pk people in another house or for a personal reason just as long as it isnt dont multiple times within a time spectra, such as a day. I mean cmon, when it rains it pours, and multiple pk's can just ruin a person's day! Hell, I remember at RL3 I lost 20 lck, a dshield, and an anchets sword all in the same day.
My $.02
-Darwin