You'll absolutely find trolling attempts in 100-Man Mario, Ben.
One example that comes to mind was a stage with a long open space that seems unremarkable, after you descend along some stairs made out of blocks (like the ones you see near the end of 1-1 in the original Super Mario Bros. game).
So you start forward from there, and you jump, but you hit an invisible block. So you keep going, and you find out that every single place where you might jump has an invisible block over it, meaning you have to drop into a pit and lose a life before trying again. So you do that. And this time, you know you need to make a long jump to clear that lower ground in order to avoid getting trapped. So you make a leap, and there's another invisible block positioned just right so that you're knocked down to the low ground and have to lose ANOTHER life. And there are other such blocks.
Technically, the level can be completed... and in fact, I did clear it. But you have to pay the toll in trial-and-error, until you figure out where every block is.
And of course, there are all sorts of variations on this sort of thing. I've encountered a few now, after only playing through around 120 or so player-created stages. Some players are just mistaking ridiculous trial-and-error for "fun," but some are definitely trolling.
"Too often we enjoy the comfort of opinion without the discomfort of thought." - John F. Kennedy on reality
"What if everything you see is more than what you see--the person next to you is a warrior and the space that appears empty is a secret door to another world? What if something appears that shouldn't? You either dismiss it, or you accept that there is much more to the world than you think. Perhaps it really is a doorway, and if you choose to go inside, you'll find many unexpected things." - Shigeru Miyamoto on secret doors to another world