How can the sensitivity of capacitive touch sensors be limited?
digitalRead(pin) is the wrong way to read capacitive touch inputs.

In the file from the example you linked in your answer, the reading is made by calling CircuitPlayground.readCap(pin, num_samples) and then the returning value is compared to a threshold.

const uint16_t TOUCH_THRESHOLD = 300;

...

if (CircuitPlayground.readCap(Fire) &gt;= TOUCH_THRESHOLD) {
   Keyboard.write(KEY_SPACE);
   Serial.println('F');
}
...


You can change the sensitivity by changing TOUCH_THRESHOLD. You could also add and fiddle with the second argument to change the number of samples.