We think it works this way: if you send a message to Person A and cc to Person B, Person B thinks they're the only one who got it, but Person A sees that Person B also got it. I wonder if this can be changed so that it works like in Email -- namely everyone sees who else got it. That's what you have bcc for, blind carbon copy, or "hide cc recipients from other people" or whatever that's called. The thing seems to be doing bcc by default.