From Divinity Engine Wiki
- call UserSetFlag((CHARACTERGUID)_Character, (STRING)_Flag, (INTEGER)_DialogInstance)
Sets the flag _Flag on _Character and on every other character controlled by the same user. The _DialogInstance parameter can be examined when catching the corresponding ObjectFlagSet event, but is otherwise unused.
- This call is equivalent to setting _Flag as an object flag on every character controlled by the same user as _Character, including the triggering of ObjectFlagSet events.
- Unlike PartySetFlag and unlike UserGetFlag, this call also works if _Character is an NPC (in which case it will set the flag only on that character).