I realized why Riot added a laugh to Singed's fling now
It's just to further demonstrate how much they fucking despise this champion. In the Fiora matchup, more savvy Fiora players in Diamond III - I range I play in can actually parry the instant they hear the laugh which is triggered half a second before the animation of fling. There isn't much unpredictability at this level of play when it comes to this now, and I even tested it. This was implemented just for Fiora.