This is an interesting idea, and I find it thought-provoking. First I want to answer you. At least I like this subtle change of environment.
So, what do you think about adding a "chat symbol" (as shown in the picture
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) above the character's head to replace the exclamation mark "!"?
I have thought about it seriously, and my reason is: chat symbols are more likely to be seen as dialogue or inner activities in traditional RPG games; while exclamation marks may be seen as pornographic content or other important events involving tasks. But you don't want the latter. The specific performance of other NPCs is actually the so-called "side description", which is used to set off the main plot and characters, so that players can get a better plot experience or enjoy being cuckolded.
If this is the case, you can do it boldly. I will support you to add new dialogue texts generated by these NPCs as the situation develops! These will make the game content richer and more layered. If the player doesn't like it, then he can choose not to read it, which is the player's freedom; if he likes it (like me), he will try to read it all, just like collecting all the achievements of the game, that is enjoying excellent works. I believe someone will be willing to do this.
Anyway, kudos to you for your work! Looking forward to playing it.