Playing with "communication outside the game" rules

[Umlaut]

I'm sort of interested in running a game or a series of games that messes around with the "no outside communication" rule, and I'm trying to figure out just what kind of changes I can make that will actually lead to interesting play. I'd love to get some ideas here and maybe some links to other games that have modified this rule with interesting results.

The two things I definitely don't want to mess with are

• no communicating once you're dead, and
  
• no communicating with non-players or where non-players can see.

Beyond those I'm wide open to possibilities.

As one example: for those of you who don't play Town of Salem, there is a means in that game to "whisper" to other (living) players during the day. Everyone is informed that Player A whispered to Player B, but not what was said. This seems like something that could be interesting here,

except

that I have no idea how to implement it... the only means I can think of would be to give every pair of players a PT and make an announcement in-thread whenever they use it, which sounds pretty extreme and ridiculous (a 13p game would require 78 PTs). Any better ideas than this?

[Umlaut]

Actually the whispering effect could be achieved without PTs, by allowing PMs between players so long as I get a copy. I worried for a moment that once I allowed PMs I'd have to worry that people might send them in secret, but I

already

have no way to stop people from sending PMs so this comes down to "either you trust the players or you don't"