What if Chara is passive in a pacifist or neutral run because they doesn’t want to creep Frisk out? I mean suddenly finding out you you have a ghost in your SOUL would be creepy. Even if they’re a helpful ghost.

passivechara:

You’ve fallen in a hole on the cursed mountain, a talking flower nearly tried to kill you, the mountain is full of monsters, and there is this voice reading stuff and describing things for you while you explore.

They seem helpful?
A bit snippy at times, but helpful.

For the sake of your mental health,
It’s best just to accept things as they come and move on.