I agree that if you want to play a very cautious character you probably don't touch the creepy portal, but I wonder if this really is a frequent occurrence.
In a similar vein, if you play as Astarion, the narrator tells you that Lae'zel smells tasty after you free her and she rules out controlling the tadpole as an option. So in one play-through I took this as encouragement to kill her, while in another I simply took it as a description of my character's state of mind and resisted the temptation in order to keep a strong ally. The narrator offers descriptions to create an atmosphere and it's up to you to react to them. For some the portal might feel too dangerous too to touch, for others the slight danger might feel exciting.
