Designated Villain: Graham. For some reason some fans still believe that he's the one who gave Hayate the Book of Darkness. Which is not true, Hayate already had the book before he discovered her.
The Yagami family as a whole is very popular among the fandom. Hayate being a fan-favorite, and the Wolkenritter being very popular and the Unison Devices being also very liked, it's not surprising why there are so many fanart about the them.
Growing the Beard: For the entire franchise as a whole. While the original show certainly had a lot of memorable moments, the series was still coming into its own and had a lot of teething problems; A's is considered the point that the Nanoha franchise truly hit its stride with the series mixing in the best of both worlds from its Magical Girl beginnings to its Super Robot / Space Opera roots, keeping the majority of the supporting cast from the first season around as well as introducing new favorites, and all this atop the season's intriguing Grey-and-Grey Morality. The season was so well received that every entry in the franchise from this point forward has had to follow in its shadow.
Reinforce: (To Nanoha) You will understand someday, when you meet someone who you love as deeply as the sea, and want to protect their happiness.
Nanoha: (To Vivio) As long as you're smiling and happy, I'll always be smiling and happy, too.
Jerkass Woobie: Vita, before meeting Hayate, was a jerk even to the other Wolkenritter as shown in the sound stages, and harshly rebuffed Reinforce's efforts to reach out to her. She who also the one who seemed to suffer the most from a life of constant fighting.
Narm: In retroperspective, Signum's voice was higher in early episodes, which can feel rather odd. It became deeper after a few episodes, even though not as deep as she sounds today, but the odd feeling is not as strong than in the early episodes.
Rooting for the Empire: Done intentionally. The Wolkenritter are likable antagonists who go out of their way to avoid killing people, so the audience is meant to want to see them succeed in saving Hayate.
We never find out how Hayate reacted to hearing about Graham having planned to use her to seal away the Book of Darkness, or if she ever found out at all.
Kyouya and Miyuki are shown to be expert swordsmen in Triangle Heart 3: Sweet Songs Forever. One of the enemies their sister is fighting in A's is a sword master. Despite the obvious opportunity for a duel between Signum and either non-magical Takamachi sibling, the most significant event featuring those two in that season is Miyuki ribbing Kyouya about his love life.
Considering how much Vita prides herself on there being nothing in the world she cannot break, why didn't she ever seek out a rematch with Yuuno Scrya, the boy who — without any Device and lacking her centuries of combat experience — managed to fend her off entirely without even giving her the dignity of his full attention? There's no way that he wouldn't have infuriated her, and no way she would have forgotten or forgiven the offense to her pride. At the very least, she should have become the SECOND antagonistically snarky bane in his life, after Chrono.
Tough Act to Follow: A's serves as this for the entire franchise itself as every season post this one is often debated upon whether or not it lives up to the originals potential or if it falls flat.
Viewer Name Confusion: Liesearia and Lieselotte have Only One Name, but some fans mistake Liese for a surname due to them going by the nicknames Aria and Lotte.
Wheelchair Woobie: Hayate, whose inability to walk is less of a concern to her than her loneliness and potentially shortened lifespan.
Woobie Family: About half of the drama in the season revolves around how cruel destiny is to the Yagami family.
YMMVs introduced by the movie:
Broken Base: Considering the fact that this is a Compressed Adaptation of the most beloved story in the franchise the movie was bound to run into this in some ways.
Either you loved it for the visuals, Fate's development and Fate and Nanoha's friendship, or you hated the movie due to bland music and fight sequences, Yuuno basically being written out of the movie, Lindy and Chrono never getting any closure to what happened with the Book of Darkness as well as the fact that the Wolkenritter held onto both the Idiot Ball and the Conflict Ball just to make the plot work.
About the only things universally praised by all fans in the movie was the cleaned up visuals, fight against NachtWal and Reinforce's device being cool. However, the first action sequence is also universally disliked by fans most likely due to Nanoha and Fate getting completely Curb Stomped by the Wolkenritter.
Visual Effects of Awesome: Regardless of the fandoms feelings on the overall quality of the film the one thing that is universally agreed upon is that the visuals look amazing and help elevate the action scenes far beyond what the original anime could produce.
