I never put much thought into how inserting my Diva worked because I always thought it worked perfectly.. But my last period had it leaking nearly every time because it wasn't opening! I use the punch down fold and it was completely folded inside me, and it was so tight in there that it didn't leak for a while, what could get in through the slits on top (inside the folds) did, and whatever else just sort of sat in the outside fold of the cup until I fluctuated some sort of way enough for it to leak. Even twisting it around didn't do anything.
So then I thought to try inserting it upside down. Not inside out, but with the folds facing my behind and not my pubic area. It opened just fine then, but when feeling around, if I pressed on the cup at all and any air escaped, the seal would go back, but with a fold in it. Like oblong shape. If I accidentally pressed more, it would just seal across, like a flat sealed shut line.
I'd just never thought of having to have it full of air in order for it to open... but I suppose it makes sense!
What direction are your folds when inserting? Does it make a difference for most of you? I find it nearly impossible to do anything with the pubic bone in the way...
And good news! I had no problems at all with removal during my last period! No problems whatsoever! It sat low all through!