The banana plugs are the leads to the power supply, which is the connection method used for most battery chargers. Leave a battery plugged into any charge adapter and pull the plugs from the charger and you have a great chance of shorting the battery. If you plan on connecting to the adapter to use the balance tap to check cell voltage at least have the sense to place some type of insulating cover over the exposed banana plugs.
As for a small spark being generated when connecting the battery to the adapter when it's connected to a live charger, this is something that is very common when connecting a battery to the power supply of a multirotor as well, regardless of connector type, and why some install capacitors in the power circuit.
Batteries are pretty dumb things, accepting and releasing energy during some relatively specific conditions. We need to be smarter than the battery.