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.
YMMV: Dumbledores Army And The Year Of Darkness
NOTE: This page has its very own Discussion Page. If you click the Discussion link, it will take you there and not to the primary discussion page.
Alternate Character Interpretation: The DAYDverse is just full of this, affecting every significant character and even some very minor ones.
Author's Saving Throw: A common complaint about the first story is that Crucio is demoted from being a nightmarish torture to the equivalent of flogging - the students take to bragging about how often they get cruciated. As if catching on himself, Thanfiction wrote a scene in Chapter 21 of the first story where Neville, facing Bellatrix, gets hit with Crucio - and thinks to himself, just before he whites out from the pain, that the Carrows never did a proper Crucio.
Severus Snape. As Headmaster, he inflicts his sadistic whims on the poor students and regularly blackmails the D.A. by punishing eleven-year olds in their place. He even ordered an eleven-year old flogged and left in chains for thirty hours. What Snape did to Michael as a punishment for freeing this kid was completely unforgivable: he had the poor guy tortured in a nightmarish way, prolonging the agony to the point where his best friend Terry tried to put him out of his misery with Avada Kedavra. The author has been criticized for portraying Snape as way, way too evil.
The Carrow siblings, Alecto and Amycus. The former makes her students repeat hateful anti-Muggle propaganda in classes and tortures them with the Cruciatus curse if they refuse. The latter is even worse: he over-uses the Cruciatus curse as a punishment to the point where students are not afraid of it anymore. And let's not forget how he forced Hagrid to throw Neville, Ginny and Luna to the werewolves.
All villains from the canon are portrayed as even more monstrous, since this story is Darker and Edgier. Of course, Complete Monster villains like Voldemort and Bellatrix Lestrange are way, way worse in this story.
"Professor" Hans Belsen, named for the Belsen-Bergen Concentration Camp. If Grindelwald is an Expy for Adolf Hitler, then Belsen is an Expy for Josef Mengele.
The Diabhal Dubh in Sluagh. He makes all the previous villains seem like Care Bears.
If Thanfiction knew enough about Demiguises to include them in DAYD, he should have known enough about them to not portray them as invisible goats when they're invisible apes.
Jerk Sue: This is the heart of the Fandom/Hatedom split.
This story's Neville never thinks of his friends as friends, just as assets to be used in the war. This is supposedly why he's such a good leader - but it's completely the opposite of the Neville we know from the books.
Everyone fawns over him. Even when he's acting violent and irrational. Hell, even in chapters where he's evidently meant to be in the wrong, others apologise to him.
For example, at one point, he's literally killing himself through pushing himself too hard, and is lashing out at people left and right. The rest of the Dumbledore's Army leadership decides to tell him he needs to step down for a few weeks, and that they won't take no for an answer, carefully explaining that it's for his own good, and that they look up to him, admire him, and look forwards to his return in a few weeks. Cue several chapters of Wangst, constant whining and despair that he's lost Dumbledore's Army! How could they do this to him, etc, and throwing as big of a temper tantrum as he can. The other people apologise (with much suppressed eye-rolling) for having dared to look after his health. He never apologizes to them.
Ron the Death Eater: Snape is portrayed as being considerably more evil than in canon in this story, with this essay by the author interpreting him as an unrepentant sociopath looking for an excuse to murder and torture students. Even considering that he's a rather unpleasant Sadist Teacher in the books, the logic taken to reach this conclusion is... somewhat debatable given the textual evidence.
They Wasted a Perfectly Good Plot / Shaggy Dog Story: Chapter 18 of DAYD. Hans Belsen, basically an Expy of Josef Mengele, shows up to the school because he wants to torture children. When Neville and Jack Sloper insult him later that chapter, he immediately leaves the school instead of, you know, torturing them.
"BAM! Other side of his face goes, and Alecto was so furious, she kicked him out of the class. Said he had lost the privilege of learning from Belsen. So that's when I raised my hand and asked if I could lose the privilege too, and Belsen just gave the whole class this long look, looked back at Alecto, and told her that he had been under the impression the teachers controlled Hogwarts, not the students, and he left." — Jack Sloper describing the surprisingly quick defeat of Nazi torturers.