My initial intention was to simply tell the tale, and as I've told Lore and Smoke, that incident was something that I actually saw happen before my eyes back when I was a newbie skydiver. I didn't know any of the people (then), but I was utterly shredded by the event, almost to the point of giving up the sport. I later became friendly with the 'real life' "Lee", and she was (and probably still is) wracked with massive guilt at not being able to help the guy.
I, too, loved Severus' transition very much, and yes, I did want it to hit people hard, and make them think about how arbitrary death (and life) can be, and that it doesn't matter how much we want to die or want to live, or how happy or unhappy we are.
As for the warnings, which I think were the crux of the dissent, I can see where readers might want more warnings/more specific warnings, but I still think that doing so would lessen the impact of the story. I'd thought of changing the outcome, but every word I wrote to that end felt like a lie. I guess it is what it is.