These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Family Unfriendly Aesop: Franz Bonaparta's books contain plenty of these like, "Sometimes you're simply screwed no matter which choice you take."
Genius Bonus: Aside from the extra understanding gleaned by those with medical degrees, there's a bonus for film or animation students. Lipsky could be a puppeteer just because it's a part of his character, or because it's both creepy and sad...or it could double as a Shout Out to the Prague school of animation, which, based on when Monster is set, would have still been going strong during Lipsky's childhood. This particular localized trend produced a lot of work based on puppetry and dark fairy tales, both elements which compliment Monster nicely. And of course, Lipsky's first met in Prague.
Like You Would Really Do It: Will Tenma actually confront the problems of his Thou Shall Not Kill code? Of course not, don't be ridiculous. Possibly subverted by the finale, however. If Johan escaped to continue his rampage, it wouldn't do Tenma's idealism any good.
Johan skips right past it in the first volume and keeps going from there.
One could even say that this series doesn't have one. People are redeemed (sometimes at a large cost) for crimes so heinous even death wouldn't be enough in most series. At the end, even Johan is forgiven by his sister, who says "Even if we were the only two people left in the whole world, I would forgive you."
One of the main themes of the series is the question of whether or not the Horizon even exists: is there a point where a person is so far gone as to be truly irredeemable?
In the end, the answer is a mixture of yes and no. No one, not even Johan is truly beyond redemption, but what makes Johan irredeemable is the fact that he doesn't want to be redeemed.
Even this is ambiguous as Johan's lack of desire for redemption seems to stem from his belief that he is irredeemable. "Some things can never be amended."