I think it's worth having a real conversation about good-aligned PCs killing good NPCs, and the consequences of that.

I will start by saying I agree that for years, it was entirely ignored to the detriment of RP.. it was at the point where it simply didn't make sense. A good person should never mow down a bunch of innocent people (even if they're aggressive), without showing any kind of remorse.

But I think we've taken a step too far in the other direction.

I think good PCs killing good NPCs falls into a few different categories, and ech one of them should be treated differently.
1. Good PC intentionally killing good NPC.
2. Good PC accidentally (but through their own fault) killing good NPC.
3. Good PC killing a good NPC through no fault of their own.

Here's my opinion on how those three categories should be handled:

#1 is pretty clear-cut. That would need some really significant justification to be acceptable. Alignment-dock or some heavy redemption efforts would absolutely be required. That's a very bad thing. I'd go so far as to say this could be an auto-uninduct from Fort, even. This should be a very hard road to come back from - that said, I think this is extremely rare.

#2 should absolutely result in that good PC feeling guilt, seeking redemption and trying to "atone" for their mistake. This is how most good NPC kills are handled, and when it happens (ie, you kill an elven "boy", instead of the dark-elf necromancer "Boyardee"), they should respond appropriately. If they don't, Imms should step in and ensure that they do.

#3 is the point of contention. This would include mobs being shoved into goodies, aggro good mobs dying in one round, etc. Depending on role, most good PCs absolutely SHOULD feel some level of guilt and responsibility. But that should absolutely never be imposed by others. Think about how this would work out in real life - you wouldn't tell your friend that it was their fault and they should feel guilty when it wasn't. You'd tell them that it wasn't, and that they should be angry at who really was at fault not at themselves. This should absolutely never involve Imm/leader-mandated redemption arcs, or anything along those lines.

This isn't just because it's not necessaruy, but it's also absolutely terrible roleplay for most good-aligned PCs (be they mortal or Imm) to tell another good-aligned PC that they should feel guilty because someone else did something wrong. It is not good behavior to force someone to feel guilty and depressed for someone else's actions. It is not good behavior to tell someone that they should have predicted someone else's evil actions.

Think about it - you would absolutely applaud an evil player for making a good player feel guilty about something, wouldn't you? Because it's absolutely EVIL to make someone feel guilty about something they didn't do. Can we please stop pretending like it isn't?