The creation of items that we don't understand is one way that we break causality. We can create something that (presumably) no one has ever created before (e.g. a healing gauntlet or a magic enhancing gauntlet). And then we can use it or reverse engineer it to figure out how it works. The order of these operations is wrong according to a conventional understanding of causality.
But the biggest violation of causality is our casual use of grief control. The normal chain of cause and effect transforms human girls into magical girls who use magic and accumulate grief. A fraction of that grief can be offloaded onto grief seeds to delay the inevitable, but (inevitably), the grief will accumulate until the magical girl transforms into a witch. However, our abilities allow us to shatter the normal relationship between cause and effect by being able to control both the cause (magic) and the effect (grief) simultaneously without cost and without limit. At the beginning of the quest, I was worried that there would be some hidden cost that we hadn't anticipated, but this does not seem to be the case. The kind of power we wield is goddess level, so I can only assume that it was the result of intervention from a goddess.
Madokami is the biggest example of causality violation. She absorbed the grief from all witches past, present, and future (including her own) and then abandoned normal causality so that she would be able to fight and destroy the resulting witch.
Homura is also an example of causality violation (as well as the basis behind Madoka's power), but she had a lot of trouble actually making any of her changes stick. All magical girls break causality to one extent or another in defiance of the normal laws of entropy (that's why the incubators want to collect energy from all of us). But some powers are more bullshit than others and ours is the most bullshit power I've ever heard of apart from Madokami's.