Also relevant to this is that people have really different ideas of what constitutes multi-killing. (Often people also have very different ideas of what constitutes multi-killing when done to them vs. when they do it to others.)

I think someone who keeps right on someone and tries to kill them again as soon as they unghost without a very good reason has been pretty consistently frowned upon and isn't very controversial -- but this is a very very rare case in all honesty.

To me, the dictates of sportsmanship are: if you looted the hell out of someone or know that they were cleaned out by someone else, you owe them time to regear. Also, if they're trying like hell to stay clear of you, you owe them the chance to do it for a while.

And... that's about it.

If you kill someone and they continue to try to raid your cabal or retrieve from your cabal, I think you're justified in killing them.

If someone you kill attacks you again or comes at you, I think you're justified at killing them. I don't think you owe them the chance to sleep you or summon you into a locked room or whatever first.

If your Outlander ranger kills a necromancer getting XP in Emerald Forest and they just go right back to getting XP in Emerald Forest, I think you're justified in killing them again. They know you're there, they know they may well be outmatched and they're not even trying. I don't think it's good for the game to pity brigade on them, first because I don't think this behavior is conducive to improving and becoming a contender, and second because this behavior is attempted by passive-aggressive veterans looking to win a log board victory much much more often than by actual newbies.

If someone attacks your group of three and kills one of you, I don't think you should expect that they now for some reason have to back off the whole group and let you level in peace.

If someone tries to raid your cabal and kills you in the process but maybe isn't in a position to finish the raid before you unghost, I don't think you should expect that they won't come back.

But I see people cry multi-killing on each of these scenarios regularly, so clearly opinions vary.