In relation to how the story discusses how idols/celebrities assume personality archetypes and images in order to appeal to audiences, and that the protagonists use their personas to perform during the songs, one could say that the main characters are using stage personas.
At first it Kanami seems like your regular Cute Clumsy Girl stereotype, but some things are off, the clumsiness is played a lot more serious with her and she seems genuinely aware of and annoyed by this trait of hers... Then she mentions in her inner monologue that she is prone to low blood-sugar and needs to carry around dextrose with her and suddenly, everything makes sense. Her being The Klutz isn't supposed to be a joke; it's her genuinely struggling with poor health.
It's a well-established fact that most electronic devices - especially telecommunication - don't work properly in worlds and areas populated by Shadows, so how are the Kizuna FES audience sending each other text messages on their phones while on the Midnight Stage? ...Well, think back to Rise's inner monologue during Chapter 3. She outright stated that all forms of "conveying" and "communication" are far more effective on the Midnight Stage to the point that it has had an effect on her Persona abilities. In other words, the phones, as a means of communication, are able to forego the need for a provider (which they are cut off from) on the Midnight Stage and directly "connect" with each other, as long as the sender and receiver of the messages are both present on the Midnight Stage!
The fact that Kanami's official artwork has a star in her eye which, considering she wears contacts on stage, may be a specific choice by her agency. Also, it could be used to mean 'Starstruck'.
Remember when Tomomin becomes a Shadow and she wears a butterfly mask? Or how about that her personality and traits (laughing fits and forgetfulness) are similar to Yukiko's? If you know the Shadow Types in Persona 3 & 4, Priestess Shadows wear butterfly-like masks. And what is Yukiko's Arcana again? The High Priestess. This means that the developers planned Tomomin to be a Priestess-type character (or shy and reserved).
As quite a few fans pointed out, Adachi's DLC is essentially an interpretative dance version of his own story with the Investigation Team and Inaba. Take a closer look at his moves and even the stage he's in and you'll see they're referencing different parts of his development:
The way he enters the stage is with his arms outspread, which is also how he enters his boss battle in Persona 4. During one of the central portions of the song, he'll point outwards repeatedly with an angry expression, a move he does, again, during his boss fight when he's taunting the party.
A few of his dance steps are taken directly from the other characters, except done in a way that's a bit more silly and loose, fitting with Adachi's mocking attitude towards them.
Another kind of dance move he uses frequently, especially during the somber portion of the song, is to move like a puppet or as if he's restrained. He was used twice by higher powers to carry out their whims - namely Izanami through Ameno-Sagiri and, to an extent, Sho Minazuki - and therefore was doing what they wanted even when he didn't realize it.
Yu is the only dance partner available for the DLC track. Adachi and Yu are foils to each other, something that every spin-off involving the two together references just as much as the main game, and it translates into the dancing too. Their Fever moment is less like dancing and more like a choreographed fight scene between the two, with Yu even offering his hand to Adachi as an offer of friendship that he promptly smacks away to continue "fighting", and finishing with the two back-to-back with each other.
Finally there's the stage and the song themselves, Yomotsu Hirasaka and a remix of "The Fog", both of which belong to Izanami, the True Final Boss of Persona 4. While Adachi is the final boss of the main story as the killer, his powers are a result of Izanami's own influence through one of her aspects, the monster Ameno-Sagiri, who controls the fog in the TV World. Fittingly, the remix used for the dance includes a short guitar riff that's also present in Adachi's boss theme, "A New World Fool".
A Meta case. The reason for Nanako having one of her costumes dummied out was that Persona 5 was almost releasing around the same time as the game, but, when it was delayed to around a year later, the costume became a spoiler that they had to cut!
On the subject of Rise, it's been noted that her in-game dancing, while not bad, is not as intense and complicated as one might expect for a professional performer like herself...until you remember that, as an idol, Rise would be performing her choreography while singing, a much more difficult feat than just dancing on its own. Therefore, her choreography is less intensive to reflect that aspect of her performance!
The game's opening song, Dance! has some references to Pursuing My True Self, the opening song of the original Persona 4. Aside from being a nice Book Ends, the lyrics also show the Character Development of the singer (presumably Yu and the rest of the team). For instance, Pursuing My True Self ends with "I'll search for your heart, pursuing my true self", while Dance! begins with "Got me something true now, I'm not looking anymore". In the former song, the singer is a confused person struggling with his life, just like the Investigation Team in the original game. Meanwhile, the latter song is about how the singer is now content with their life and expressing their happiness, just like how the story is not about the team's issues, but about them helping others.
Fridge Logic
If this is supposed to take place after the epilogue of P4G, then why is Kanji's hair bleached again? It was shown that he reverts back to his natural hair color in the epilogue.
This is actually handwaved in the Story Mode where Yu explains that the theme of their stage outfits for LMB was to look as close as possible to how they looked when they first became friends and thus all of them put their hairstyles back to what they were like in P4. This doesn't explain why Nanako's cut her hair down again too, but it's better than nothing.
Perhaps she wants to emulate the Investigation Team? It's clear she looks up to Yu if nobody else.
Also, related to P4G, the reason why Marie isn't part of the main group, even though she's obviously in the Velvet Stage area?... You really think Marie would ADMIT to enjoying dancing?
In the secret Prologue chapters, several of the characters complaining about the heat, including Teddie - who is wearing a long-sleeved shirt in said scene, despite it being canon that he owns a short-sleeved shirt as well. Even if it was a matter of saving disk space on sprites, it's glaring that wouldn't just, you know, go home and put on another shirt if the heat is bothering him that much.
Teddie's complaint about it being too hot was that he couldn't wear his bear suit (i.e. his actual body). Thus why he's in his human body and clothes when meeting up with the team and not as mascot Teddie.
Fridge Horror
Kanami literally describes herself as a fat cow when in character. Later it's implied she has weight related body issues. In addition, she specifically mentions that she struggles with low blood sugar and carries around dextrose. Which could mean that she's friggin' pre-diabetic, and undiagnosed at that.
In general, all the girls in Kanamin Kitchen describing themselves as pieces of meat becomes incredibly disturbing in relation to the problems embedded in the idol business.
