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.
Canon Fodder: Whenever a throwaway line of dialogue is needed, one of the characters, usually Keitaro, says some variation of "...It had three holes, and I really wanted one." The mysterious object with three holes is never revealed, and is probably an inside joke among the creators.
Designated Hero: The girls all qualify. They assault Keitaro for minor offenses, and they sadistically torture his friends when they don't know where he is (see Moral Event Horizon below).
Dry Docking: At least one fan was very happy that Keitaro ended up with Naru, leaving Motoko single.
Jerk Sue: Many fans see Naru this way, due to her knee-jerk reactions to whatever Keitaro does; made worse since it's usually unintentional. Yet, she never gets called out on it, or suffers any karmic backlash, at least in the anime (and in the manga it takes A LONG TIME to happen).
Les Yay: Naru and Mutsumi in the shower shortly after Mutsumi is first introduced in the manga.
While Keitaro is away, Mutsumi "dresses up" as him (by putting on glasses and rearranging her hair) in the hot springs and puts the moves on Naru. While the reason she gives is to merely try and make it easier for Naru to express her feelings for Keitaro, Cue Naru Megaton Punching her by mistake.
When Kanako first arrives in Love Hina Again, she disguises herself as Naru and feels up a number of the residents of Hinata Inn as research for her disguises. Motoko's "examination" takes place in an alleyway, and draws quite a crowd of nosebleeding men.
Much more discreet in the manga, where Kanako-as-Naru attacks Motoko inside the Hinata House, using the convenient pretense of privately teaching her about what could be in the entrance exams.
Moe: Shinobu. With those vulnerable eyes, luminscent blushes, embarrassed stutterings, and that impossibly cute squeal, how could anyone not want to hug her?
Moral Event Horizon: The girls cross it in the Spring Festival when they kidnap Keitaro's two friends and start torturing because they think that they might know where Keitaro went. When they beg Naru for mercy, she cruelly orders the girls to continue torturing them. Remember folks, these girls are our heroes!
Ron the Death Eater: The hatred some fans have for Naru or Motoko (or Kitsune, sometimes) reaches ridiculous levels at times...
Ship-to-Ship Combat: Put a Motoko/Keitaro and a Naru/Keitaro shipper in the same room. There will be blood.
Even worse: bring in a Mutsumi/Keitaro shipper. Say your prayers, everyone.
Die for Our Ship: Either Motoko is an abusive bitch without any sympathetic traits and wants to steal Keitarou from Naru, or Naru is a cruel Domestic Abuser who should be tied up and forced to watch as Motoko marries Keitarou.
Subbing vs. Dubbing: The Love Hina anime has a reputation amongst voice actors and fans alike for being a royal pain in the ass to dub in almost every language. As a result, pretty much every dub other than the original Japanese is disliked by the fanbase.
Special attention goes to the Mexican Spanish dub, which was so poorly received it practically destroyed the perception of the franchise in Latin America.
On the other hand, the Mexican translation of the manga is considered to be excellent, handled by the same person who translated the scripts of both Sailor Moon and Cardcaptor Sakura's animated adaptations.
The manga has two complete English translations, each with its own positives and negatives. The Tokyopop translation has a natural flow to it, but suffers from severe lack of proofreading (Volumes 2-5 and 9 in particular) as well as a Lost in Translation issue near the end due to adapting a term early on that later turned out to be a plot-important multi-level pun. The Kodansha translation by the Nibley sisters has much better editing but is rather literalist and tends to come off stilted as a result.