I've confirmed that fake death alerts have been triggered by someone on the chat channel.
It seems that it's possible for someone to just create fake messages and trigger the alerts.

Is this only a one-time possible troll because of the cache? then this would be fine.

Its a 1-time thing. There is a mechanism to require validation for messages, but that requires that the person who died is in a guild. IMO its not worth jumping through the extra hoops to stop spoofing but I'm open to ideas