Alien Space Bats: The premise, which involves an exploding Dementor somehow allowing the nominally-adult Harry and Hermione to possess their past selves back in 1991: nothing about the established properties of Dementors or Potterverse time travel implies this to be possible.
Contrived Coincidence: Any of the Weasleys would have been perfectly justified in wanting revenge on Lord Potter; in the event, the one who decided to actually go there was Percy, who Lord Potter just happened to want to kill anyway.
Crapsack World: The original timeline is so bad that letting Voldemort win would probably have improved matters.
"Facing the Bullets" One-Liner: Hermione insults Ron one last time before saying to the dementor, "C'mon big guy, I've been kissed by Ron Weasley so this should actually seem pleasant!" This is the first indication we get of Hermione's canonical badassery.
Aside from her apparently forgetting that in the book, she kissed Ron.
Fantastic Racism: The canonical disregard for Muggle-born wizards is taken Up to Eleven and beyond. Bizarrely, once Harry and Hermione arrive in the past they find the Wizarding World to be somewhat enlightened on this matter. In that case, how on Earth did Umbridge get away with keeping Voldemort's purity laws on the books?
For Want of a Nail: When they arrive in the past Harry accuses Molly of abducting him at Kings Cross Station. One thing leads to another, and eventually Voldemort is defeated (and Dumbledore's reputation is destroyed) within two months. On the other hand, this is probably less due to the butterfly effect and more to do with the fact that Harry and Hermione have information and magical ability from the future.
In Spite of a Nail: Nevertheless, Harry seems convinced that Teddy Lupin can be born in the new timeline. Considering that Tonks and Lupin get married years before they do in canon, after the defeat of Voldemort, and both of them survive, it's clear that any child they have will not in any way be the Teddy that Harry left behind in the old timeline.
Informed Flaw: The Sorting Hat didn't put Ron in Gryffindor because of his cowardice; this is someone whose main contribution to the plot so far will be to attack a witch who's provably more skilled and powerful than he is, twice, apparently just for the hell of it.
Kangaroo Court: Harry and Hermione, in their trial for killing Ron and aborting his baby, respectively. They know they have no hope of getting off, especially since the dementor is already there, so they merely decide to taunt Ron and those who put them on trial before they go.
Kick the Dog: Ron doing this sets the entire plot in motion.
Not only does the court quickly convict and sentence Harry and Hermione to death without anything resembling a fair trial, but when Harry snarkily says that he didn't think the magical government was capable of organizing this, Umbridge decides to have Hermione's sentence carried out first so that Harry can watch.
Men Act, Women Are: The events of the first chapter are driven entirely by the actions of Harry and evil!Ron, with Hermione serving only as a passive observer and victim.
Mixed Metaphor: Inevitable when you've got an author who's fond of both metaphors and run-on sentences. The scene where Lord Potter springs the rat trap in the snake's den led one reviewer to reference Mitch Benn's "Devil and a Hard Place".
Moral Dissonance: Not only is pureblood supremacy presented as being as evil as it is in canon, characters who aren't pureblood supremacists in the books are in the fic for no reason but to show us how evil they are. However, Harry loves nothing more than exercising his privileges as "Lord Potter" and demanding that everyone address him as such. So claiming you're better than other people because of the circumstances of your birth is bad, except when it isn't.
Plot Hole: Hermione apparently has enough power to overload a Dementor, but can be overpowered by a "shit wizard". It could be an extreme case of Unskilled, but Strong, with emphasis on the former, but if so then this isn't established at all.
Replacement Goldfish: Harry and Hermione seem to work under the assumption that a child born to Tonks and Lupin in the new timeline would be the same person as the Teddy Lupin they left in the old timeline, despite being born under completely different circumstances into a completely different world.
Sanity Slippage: Watching Harry continually humiliate him, resist his plans and destroy his reputation has this effect on Dumbledore. His sanity starts to slip following Voldemort's defeat, when he declares that Harry must have been possessed by Voldemort, and tries to kill him. By the end of the story, his mental state has deteriorated to the point that he's seeing a baby Fawkes that isn't there.
Scunthorpe Problem: That the fic's initials contain a profanity (assuming "and" and "the" count in the initials; in acronyms, the former is often rendered as a & and the latter is not always included) has not been lost on reviewers, especially considering the tone of its dialogue.
Sophisticated as Hell: "I am Lord Harry James Potter, last scion of the Noble and Ancient House of Potter, banisher of the Dark Lord Voldemort. Who the fuck are you to call me boy?"
Stuffed into the Fridge: Although she's not actually killed, what happens to Hermione in the first chapter serves the same purpose. Notice especially how it's Harry who takes ludicrously gory revenge on evil!Ron for it.
Title Drop: "I'll love you forever Harry, in this world and the next."
Unusually Uninteresting Sight: The only people who seem to notice anything strange about how two first years are married to each other in the new timeline are the Weasleys, who are also the only people to whom it occurs that there might be a problem with that.
Weaksauce Weakness: Apparently, goblins have the power to destroy Horcruxes... by feeding them to pigs. (Or doing something that transfers the Horcrux into a pig, it's not made clear.) They then kill and eat the pig. And Gringotts does this for a fee.