There was once a MUD which was RPE. On this MUD of whose name I cannot remember there was a kingdom with a king. This kingdom with a king had a mercenary problem and one day they stormed the castle and managed to kidnap the king. The king was killed but the tale isn't over... because you see he appeared once more memories intact and placed a bounty on those mean mean mercenaries.
Now some might say. Well if the mercenaries knew the king would rez then why did they kill him? I have no idea. The point is you can see some of the problems that MUDs specifically have had with lacking perma-death in games and not appropriately working that into their setting/theme.
If you check out that perma-death thread that Crayon linked I believe someone provided an example of how a monetized game called Gemstone III (MUD) handles death. The tldr is that players got a rez from deities and all they had to do was make sure they were in good standing which equated to leaving a donation on a shrine/alter at regular variables.
Thus the only way to die was to basically intentionally piss off a deity that you knew was rezzing you everytime you died. This was a roleplay game, I believe, and is still running. I think they tweaked their death mechanics a bit in the last few years.