A corpse turned up in my dining room (and meeting area), which I'm now trying to explain.
I routinely get elven diplomats from a neighbouring elven civ, as well as elven (for some reason) law-givers from a neighbouring human civ. Those two civilizations are at war with each other. They tend to stick around in my fort for ridiculous periods of time, which means they eventually meet up in my dining room, where they proceed to engage in spitting contests which the combat log interprets as a combat.
Where everything went wrong was when the diplomat from the elven civ decided to leave. On the way out, he ran into a werecreature and began "fighting". In elven fashion, that took the form of running about like a coward trying to get away, as I sent a squad after the werebeast.
The werebeast turned back and made a break for it before my dwarves reached it, and I took note of the diplomat's name because he has been bitten and I'm worried he might try to come back later on a (doomed, obviously) diplomatic mission.
I thought that was it, but shortly after I noticed an elf corpse in my refuse stockpile. Looking around in combat logs, it appears that two of my dwarves engaged the *other* one, the law-giver, seemingly at the same time as the other combat was happening. The first attack was thrown by a dwarf. My dwarves are armed at all times, and at least minimally trained, and the combat was quite brief.
So I'm left wondering what happened here. I know loyalty cascades are a thing that happens within your own civ, but could something similar have happened? The only hypothesis I can come up with would involve and excessively binary handling of "friendly/hostile":
The diplomat and the law-giver have been "in combat". They presumably still technically are, since both "combatants" are still alive. I order an attack on another creature who is also fighting the elven diplomat (and "helping" the law-giver), hence I am joining the conflict on the side of the elven diplomat. The law-giver thus turns hostile, and my dwarves who are chilling in the dining room react and maul him.
Is this plausible? If not, any other ideas? It might be relevant to add that this is the second law-giver to die at this fort, as the previous one drowned in my moat while I wasn't looking.