In other games I have seen people have been required to list everybody in the conversation. In some cases it would be something like Headmaster, Tae and Professor Moriarity and other case would be something like Potions Class because it would be everybody in a class. Within a classroom, potions as example again, a topic could list participants as Auric, Flander, Harada and Morganna the four people working on the assignment at the same table. The drawbacks to this one would be enforcement and making sure that nobody is using it to keep there character from having to deqal with other characters. An example of that one might be : Harry, Hermione, Ron ONLY, excluiding Neville and Padma.