The code works like this.
1) Select a random ship for the message if applicable (e.g Behind You, Praise, etc Death, Rearm, etc will have already specified a ship).
2) See if there is a message for that persona. Send from the ship from 1)
3) If 2) failed, see if there is a message for a different person. Send from the ship from 1)
4) Give up.
So if the persona doesn't have a certain message but other do the message will come from the right ship but the wrong persona. Unfortunately there is no way to change this without substantial re-engineering of the code. Which is why I suggested that if you use any new message, you make sure that all personae have that message. That is actually the way the game has always worked.