Update: 9to5google has a neat teardown explanation of what exactly happens when you insert the Galaxy Note 5 S Pen backwards, what gets broken, and why.
Let’s be completely honest. Nobody reads the manual anymore. But you should! Manuals can save you a headache or two, not to mention that they most of the times save manufacturers the trouble of repairing or replacing your broken device. An example from the recent past comes to mind with a certain Active version of a phone which often got flooded (and most of the times rendered unusable) because of not sealing the back properly, as indicated by the manual.
Some users are having Galaxy Note 5 S Pen problems. It turns out that if you insert the Galaxy Note 5 S Pen the other way around, it might get stuck, and damage the device, the S Pen itself, or even both. Some unlucky users were complaining about the issue, while others (and even the media) wrote line after line telling Samsung to up its design and functionality game.
Samsung is not only aware of the problem, if one can call it a problem, but has issued a statement. “We highly recommend our Galaxy Note 5 users follow the instructions in the user guide to ensure they do not experience such an unexpected scenario caused by reinserting the S-Pen in the other way around”. Truth be told, the manual does indeed warn users of the consequences of inserting the S Pen the other way around, so an “RTFM” statement is an easy way out of this, for now.
As far as the topic of “Samsung could have designed it to prevent such issues” is concerned, that up to you to debate in the comments below.