Aliens in Banana

Ignorance leads to fear. There is no risk having soil mites around your plant, just like there is no risk having earthworms in your soil or ladybugs on your leaves. There is only benefit and their populations are very easy to control, but they do that on their own when the food runs out. Why would you rob your plants of beneficial creatures? Fear? Very silly mindset to have.

Well, nature does work by diversity and by eating & getting eaten, so if this diversity is missing it is possible for a species to overpopulate, which can be annoying and not in our favour (mites climbing on your plants for example) You can prevent this by dusting the area around your stem and the stem itself in some diatomaceous earth though. I would not use heavy artillery to get rid of some harmless mites. Those mites are just decomposers like compost worms, they wont eat your living plants. You can even feed them the dead leaves and theyll turn it into compost. They can overpopulate though if you feed them a lot of sweet stuff like fruit, so try to keep that down. Or use that in your favour to attract and remove them with a piece of banana if there are too many or you want to get rid of them.

I don't care what people may say about them being "harmless", but I would not introduce them on purpose to any plant that I am trying to grow. Why risk it??

Looks like soil mites. Those are harmless, they act as decomposers, eating rotting plant material.