The playerlist option "Allow Mass Messages" does not save, this means that anybody who has it disabled and wants to enable it has to do so every time they login. The opposite is also true for those who may wish to disable it.
This is something I have observed from an old install, a fresh install, and it has been reported by other players.
The reason is that although toggling the check box within playerlist options writes to "allowmass=bool" within "scriptfiles/playerlistoptions", this is over-written the next time you start the client.
*Edit*
Upon further investigation there appears to be several options which are being overwrote. See this comparison of before closing the client and after re-opening it:
