I read this one fic ages ago, the title escapes me, where Ron's Impediment Jinx practice in the Gryffindor common room accidentally hits a first-year's pet Kneazle, making it stagger into the Fat Lady's portrait and setting off this whole chain of events. The prefects got involved, blame got tossed around, it created this massive rift between Harry and Ron because Harry thought Ron was being careless, and it all spiraled from a single misplaced jinx during revision. It wasn't even a battle, just homework. That's the thing about Impedimenta – in fanon, we always see it in duels, but in a school setting? It's a prankster's dream and a prefect's nightmare. A jinx meant to slow someone down can trip up a ghost, delay a message, ruin a potion ingredient delivery... the conflict comes from the mundane misuse, not the epic fights.
Writers who just use it as a generic 'stun' spell are missing the point. The beauty is in the unintended consequences. Slowing down a single person in a tight corridor during a hectic scene can cause a traffic jam of portraits all yelling, or make someone miss a vital clue. It's a low-stakes spell with high-stakes potential for chaos when you think about the domino effect in a crowded, magical castle.