Making sure the right party PC speaks

When talking to an NPC, we can use the hero of the story or any companion. This creates a dilemma or rather a stylistic fork on the road in that the author of a mod can treat the PC chosen to do the talking as a proxy of the protagonist, and then use all of the specific references like "I grew up in a library," have the NPC address the speaker as "girl" or "boy" and so forth - this is how Baldur's Gate does it; or the author can try to write dialogue specific to the speaker. When Kagain speaks, hearing "boy" requires serious suspension of disbelief. Another issue that can mess up a conversation, as I'm now discovering, is that a PC you reserve for an interjection may be the one you are using to do the talking. I'd like to know how to prevent that. For instance, the conversation may go like this:

IF ~Kagain is not in the party~ THEN REPLY ~Here, good sir, take this 100 gold pieces!~ GOTO NEXT
IF ~Kagain is in the party and in sight~ THEN REPLY ~Here, good sir, take this 100 gold pieces!~ EXTERN ~KAGAIN~ HELLNO

The HELLNO response from Kagain will forbid the speaker from giving the NPC any money - a nice touch from the role-playing perspective. But what if Kagain was the character chosen to talk, so he was the one to say "Here, good sir, take this 100 gold pieces!" ? Is he going to argue with himself?