I was playing with my MooncupUK a little while ago, and pushed it into the punchdown fold. It happened to be near my face for whatever reason and POP, it scared the crap out of me as it thwacked me on the nose. It really hurt! I'm going to try the seven fold now, I figured the punchdown wasn't so bad but I'm thinking it might be nicer to my insides not to give them a hard flick every time I put the cup in.
I'm sure it doesn't damage my insides, but now I understand why it feels so odd when it pops :P
Also: I'm inserting my newly stemless cup tonight, I'm scared! I had to remove the last piece of stem as the cup tilted and would scrape the stem on my gspot area, not fun :(. I hope for success!