A reminder PM (or email) sent out to all members would do the trick. Something along the lines of "may we remind all members that in order to avoid confusion and to ensure that guests cannot impersonate you, it would be appreciated if all members can try to log-in when posting wherever possible" The same message can be included in the welcome/confirmation email sent out to all new members.
I am but I have an advantage nobody else is quite as bad at writing as I am. Unless of course a BFC employee starts using my name, then i'm fecked.
