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.
Layton gets turned into gold at the end of Chapter 3, and Maya is locked in a cage and plunged into the courtroom's fire at the end of chapter 4. Even if you haven't seen the trailers and know there's still far more for them to do later in the game, it doesn't take a genius to figure out they're not gone for good.
As another example, like Layton would really suddenly turn traitor/villain and prosecute Espella during the last trial for no reason. It's presented as a "shocking twist" cutscene, but it makes sense in context and there are very good reasons for the scene progressing the way it does.
"Barnham! Barnham! Barnham!" After a few repetitions of that chant, you may find yourself wishing you could strangle everyone in the viewing gallery.
"SIIIIIIIIIIIIIIIIIIIIIIIIIIIIR!" Even in-universe, considered an annoyance by all. As a bonus, if Phoenix is the next character to speak (or think) afterwards, it'll be accompanied by a brief high-pitched beep to signify his ears are ringing. At one point, even Barnham's ears are shown ringing.
"BAAAAAAAAAH! BAAAAAAAAAH! BAAAAAAAAH!"note Not to be confused with the lovable talking goat puzzle.
Pandering to the Base: The whole game is a present to people who enjoy both the Layton and the Ace Attorney series, but there is no reason to put Edgeworth in the post-credits scene other than to cause a few fangasms.
The Scrappy: Emeer, thanks to his generally obnoxious personality, and due to him stealing Layton's broken-off arm after he was transformed into a gold-statue
Surprise Difficulty: Ace Attorney fans who played Dual Destinies first are probably going to be taken off guard by how much harder this game's trials are, mostly because you need to start the cross examination from the beginning even if you save during it and there's no option to just restart from the same statement with full life if you run out. (Mostly because Dual Destinies was a Sequel Difficulty Drop and thus was actually made before this game.)