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.
An early popularity poll, when only a few of the Inter-Middle participants were just introduced, has following characters in the top 10. Tenth is Erio, ninth is Corona, eighth is Caro, seventh is Lutecia, sixth is Nove, fifth is Rio, fourth is Einhart, third is Nanoha, second is Fate, and first is Vivio. It's impressive to see that Nanoha and Fate were still that popular (well, they are the original heroines), but more impressive are Lutecia, Erio and Caro, who are above Subaru and Teana.
This poll was started at the time, when the Takamachi family, Team Nakajima and the Forwards visited the Alpine family in Carnaaji.
The Smart Girl: Els Tasmin, the Meganekko who has to use strategy to win against her opponents due to her lack of power.
The Chick: Harry Tribeca, the youngest of them. She's weaker than Sieglinde, Victoria and Micaiah and has the tendency to cry often.
Hilarious in Hindsight: In the end of chapter 35, the translator makes a gag by letting Miura saying "It's my manga now, bitch!", after she defeated Vivio in the tournament. In Magical Girl Lyrical Nanoha The Movie 2nd A's Tribute Comic, all major competitors but Sieglinde and Fabia are cosplaying The Movie 2nd cast. They are later divided in the Mid-Childan and Belken teams, with Vivio opposing her friends, Miura and Harry. One could say, Miura is stealing her friends, too.
Moe: Nanoha always had a strong element of moe (before Force anyway), but ViVid really pushed it to new heights with characters making cutesy poses and winking at you every other page for no good reason whatsoever. Even twenty-something Nanoha and Fate are no exception. And looking only at the magazine posters and the artbooks you'll never guess it's a Fighting Series, and not some kind of ecchi manga revolving around cosplaying, hot springs, beaches, and generally dressing little girls as inappropriately as possible.
Also, it's mentioned at one point that the reason Vivio lacks many of the abilities she displayed in StrikerS is because her Linker Core was damaged during the battle on the Saint's Cradle. This could have been an interesting character exploration if we'd gotten to see Nanoha's reaction to having effectively magically maimed her daughter, but instead it serves solely as a blatant excuse to nerf Vivio so that she doesn't curb stomp the other girls in the tournament arc.
Unfortunate Implications: For being a manga so focused on family and friends, no one seems to notice or care that 12 year old Einhart lives alone and in her own words has always been by herself.