Either make only the main character be able to lead dialogues
And what happens if they're dead, but the NPC you just saved wants to initiate a conversation ending the quest?
There are plenty of workarounds, but it's very rare that your main character should be unavailable anyway. Dead? Maybe use a resurrection scroll?
But for an easier example, if the main character is in prison or something while everyone else is outside...
I do feel that conversations should be led by the main character, and some particular interactions should depend on the presence of the main character. However, generally, interactions should occur based on the characters present for the conversation. That is, characters all participate and interact, much like the suggestion of this thread but I don't think we should usually be choosing, as such. I wouldn't expect to
choose to let Lohse talk -- her AI should make that decision.
