You've all heard it by now: there is a pretty major flaw in the Samsung Galaxy Note5 design - insert the S Pen in the reverse direction, and the thing gets trapped by the clamping mechanism that would otherwise hold it tightly in place. We call it Pen-gate.
But why does this happen and what does the actual mechanism the holds the S Pen in place look like? 9to5Google tore down the Samsung Galaxy Note5 to find out all the details that remain invisible under the sealed body of the phone. And what it found is a lever that locks in place when you slide the S Pen the wrong way.
The takeaway is that the damage you can do by simply inserting the S Pen the wrong way is immense, and you should not try it, despite the temptation that you may feel. And yes, Samsung does warn against this somewhere in the fine print of its user manual, but this does not make this any less of an issue.