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.
Fan Preferred Pairing: Rein × Eclipse was, at least, initially more popular than the Official Couple Fine/Eclipse. In a popularity poll done by the Japanese fan community, Rein/Eclipse topped the list. Even the artist of the manga adaptation, Mayuki Anan, seems to lean towards this pairing as well since this pairing got the most Ship Tease despite that all pairings were left ambiguous in the end.
Les Yay: Sure, Altezza got paired with Auler, but there was plenty of this between her and Sophie.
Memetic Mutation: When Rein got pissed with Altezza in episode 10 of the first series, she yells, "What was that?" ("Nani yo") to which some Japanese users phonetically transcribed it as "Haniho" and ran with it.
Seasonal Rot: The second season, Gyu!, is generally regarded by fans as the weaker series due to its abundance of Filler, poor Character Development, and change in direction of the show's formula.
Ship-to-Ship Combat: Fine × Eclipse and Eclipse × Rein fans were constantly at strife. Meanwhile, interestingly, no one really cared about who Bright would end up with.