How to stop the batteries in my torch from rattling?

Wrapping them in tape is a reasonable solution, but might make it hard to take them out later. To be honest, if this bothers you you should buy a better torch. Get a Maglite or something with higher build quality. Wishing you many happy years of rattle-free illumination.

I fold a strip of piece of paper in half and insert it down the tube. It snugs it between the sides of the batteries and the wall of the torch/flashlight. I can pull it out before removing the batteries.

I do not know if this is hazardous if the batteries begin to leak from old age, or if the paper could burn if too close to the contact points of the light and the batteries. I am ignorant of these things. Perhaps follow the advice of someone wiser than me. :)

The strip of paper is a great idea. Nothing in a flashlight should get hot enough to burn paper.

I ill go along with the tape plan. Just don’t make it too think of a layer.