How do I keep split rings used for keeping keys together from snagging on clothes, thereby damaging them?
The keyring in the photo above is an extreme example of their ability to destroy clothes: The smaller ring has bent ever so slightly, causing the one end to easily insert itself into all sorts of fibrous materials and tear them apart with glee.
Of course, the best way to solve a problem is to avoid it, but there are some cases where this is not feasible: For example, although you could keep their keys in a bag instead of in their pocket, when you take them out to use them and happen to be wearing knit gloves because it's ridiculously cold (so cold that you would never want to take off your gloves just to use your keys), you can easily snag your gloves on the keys and then ruin them.
Now, I could theoretically just replace this ring with a thicker one, but thicker ones can do it as well (albeit not as frequently). In some cases, I've also simply put some electrical tape over the ring so that it no longer has any sharp edges, but then I can no longer quickly take the rings apart (I would have to cut off the tape and then re-apply it), which destroys one of the main advantages of such a design.