Note that not all events are the same - some are local and some are global. Events like created will occur on all computers when a thing is created. Events like activated only occur on the computer of the player that did the activating. So when the 0x40 flag is used, an event message such as activated will only run on one of the computers in the game.
The engine will assign this flag to all item and class cogs by default. For most item and class cogs, this is the way it should be. By running locally, they can avoid excess communication with the server.