So, I’m not really a PvP person. I dabble a little, mostly to get past transmog, but I never use WM.
During the Pre-Patch event, I’m playing a fire mage and I suddenly get an Honorable Kill. I assume an AOE killed a low level person leveling in WM?
I thought you had to opt in. Or does accidentally killing someone suddenly opt you in for a bit?
Interesting. You are supposed to need to opt in. That’s the whole point of war mode. However I know for certain some passive aoe abilities bug out and will hit enemy players already flagged for pvp, and pull you into being pvp flagged as well.
I first experienced it on my enhancement shaman in early dragonflight. I raised it in the bug forum. Several times as it continued to occur throughout the expansion. It was still occurring during superblooms, so it was never resolved. Not sure about now.
Found my thread about it.
Hmm…I wonder if it’s the old Cata bug where some spots in the world would auto flag you and make you targetable by other players. 
Maybe report it? If it is a bug probably should get that fixed.
While war mode and PvP flagging outside of war mode are separate, may require more information to determine the cause.
Were you perhaps anywhere near Hakkar’s event? My only guess is that you had the bouncy corrupted blood debuff and one tick of passing it over may have been enough to unalive someone who was already low.
I was doing Hakkar!
Still, does passing a rebuff count as PvP?
I don’t know, the debuff that gets passed around does do damage to nearby players but you would likely know more than me if you got a PvP flag from it, considering the hectic nature of things I never found myself flagged during the event.
In one of the camps by the daily quest NPC there’s a horde flagged NPC that you can easily obliterate without even knowing or meaning to. Thus flagging yourself.
That’s not warmode, but anyone on the opposing team that was also flagged could then be caught in your AoE.
Every single time I do onyxia my war mode automatically turns on…. How do I know this? I get dark arcangel while I’m fighting her…. And war mode abilities have been happening to me since event so idk
Was it searing gorge? Possibly flagged by hitting an npc maybe and not know it?