One of Koishi's regular melee attacks in HM is a sneeze.
Being Koishi, she confounds predictable gameplay by randomly stifling the sneeze in exactly this way.
Added to Gameplay Mechanics.

She doesn't randomly stiffles the sneeze. The sneeze is called by the dial 66B. Should you use it twice, she will stifle the sneeze. Otherwise she will sneeze.

MinimalMaximal said:

She doesn't randomly stiffles the sneeze. The sneeze is called by the dial 66B. Should you use it twice, she will stifle the sneeze. Otherwise she will sneeze.

I must be double tapping a lot without realizing it, then.

OtomeSound said:

I must be double tapping a lot without realizing it, then.

You mean you're doing it...
*dons sunglasses*
...subconsciously.