One explanation is missing: the angle of the edge.
If the blade edge has been sharpened to 20 degree angle, it has the same 20 degree cutting angle when used diagonally. The effective cutting angle decreases in the direction of the cut when you rotate it. The smaller the angle, the sharper the knife.
One colloquial term for the guillotine was (is?) "le rasoir national" = "the national razor."
Other colorful terms include "the regretful climb", "the silence mill", "Capet's necktie", "the patriotic shortener", "half-moon", "timbers of justice", and "Charlot's rocking-chair".
Mainly because the slicing motion separates fibers in the fresh, it's more effective than blunt force. Same with a knife.
It's interesting, however, that this post is much higher on the front page than the post about Durov's arrest by the French ever was, despite having 1/10th the number of comments during a similar time period.
You then have to ensure the flat side of the blade pair meets without a gap. The gap, at least when I’m sharpening wood planes with a chip breaker, allows material to get stuck which will prevent a good cut. I would imagine getting some spine caught in a gap there would cause issues. With a single blade you don’t need to worry about the back flatness as much.
Unlike cigar cutter on which you apply a constant force, a ^ guillotine has fixed potential energy. It will get to the toughest part of the neck when bigger portion of it is spent, so it may or may not be enough to cut trough.
True. But it may lead to some amusing situations - like when you are having a zoom call with people from all over the world to be at a disadvantage because you are native speaker or have C2 Proficiency in English.
Many are. Scissors, drill bits, even the way most people use a kitchen knife, they put as much force onto as small of area as possible. At certain differences in scale it won't matter (razor blade vs a single hair), but how a cut is performed is definitely part of the design process.
Only those that go in frames. The angle is applied while using proper cutting technique for knives. A flat blade would also go dull rather quickly, as only one portion of the blade would be doing all the cutting (well, tearing, a straight drop with a flat blade would be like trying to chop a tomato rather than slicing it).
If the blade edge has been sharpened to 20 degree angle, it has the same 20 degree cutting angle when used diagonally. The effective cutting angle decreases in the direction of the cut when you rotate it. The smaller the angle, the sharper the knife.