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.
YMMV: Anohana: The Flower We Saw That Day
Awesome Art: The manga adaptation, which accurately recreates, and even improves some of the frames from the anime.
Jerkass Woobie: Yukiatsu may be an elitist asshole who lives to show Jinta up, but Menma's death left him a whole mess of emotional issues and he does realize how pathetic he is. He does start to get a bit nicer after he is outed as the fake Menma.
Moe: Menma. Also the kids when they were young and Menma's little brother.
Purity Sue: Menma. She has a million good qualities and no real significant flaws. She's selfless, pure, beautiful, innocent, loves everyone unconditionally, and is loved by all in return. Tsuruko and Anaru want to be like her, and Jintan and Yukiatsu are both still deeply in love with her even though she's been dead for years. This can be explained somewhat with her being, well, a pure and rather innocent little kid even by normal standards before her death, and literally not being able to change or mature from there.
She may be a Purity Sue, but she also works as a deconstruction of the trope. Not only was Menma ridiculously pure and innocent (and kinda ditzy) because she died as a child and thus got mentally/emotionally stuck as a little girl forever, but it's made brutally clear how much pressure that kind of character would put on her friends: Tsuruko and Anaru remember Menma fondly but are also jealous and resentful of her because she (unintentionally) left an insanely high standard for them to meet when she kicked it; Jintan and Yukiatsu are very screwed up due to still loving her for a long time after her death, with Jintan unable to function in social situations and Yukiatsu cultivating an unhealthy obsession; and Poppo constantly has to put on a happy face in order to interact with others due to his guilt after not being able to save her life.
Was anyone else a little weirded out when Poppo invited Jinta on a "Jungle Cruise" while pulling down his pants?
Seeing Yukiatsu sniff out one of a sundress that he bought which looked very similar to the one Menma used to wear weirded out quite a few people. It got weirder when he used the dress to crossdress as Menma.
Stoic Woobie: Tsuruko, although she doesn't seem like it until much later on.
What an Idiot: Both Jintan and Menma fail to just have Menma prove her own existence to everyone else by simply lifting an object or two in someone's direct line of sight. It's especially noticeable at the end of episode five, when Poppo is intentionally seeking out Menma because he wants to help her grant her wish. Instead of trying to interact, Menma cries over not knowing what she wants to do and instead wishes that she could talk to her friends, leaving Jintan to angrily tell Poppo to stop. It doesn't help that Menma ended up revealing herself in such a way in episode eight.
It's somewhat more understandable when Menma says she has tried to do the same thing in her house, but it doesn't always work. (And it's speculated that this may be because her mothers's grief is too intense to allow Menma to contact her — "Mama gets really sad", remember?). She could have simply assumed it wouldn't work with her friends either, specially considering how much they changed and grew apart after her death, and episode 8's revelation scene came during quite the crisis between the former Peace Busters so she likely used it as a desperate measure.
Jintan has a subconscious desire to keep Menma to herself here amongst the living that he struggles with, and thus monologues that he doesn't really need to think about it; Yukiatsu later discusses this possibility with the rest of the gang after Menma's ghost is proven to be real. Menma simply desires to stay with her friends and also monologues that she doesn't really need to think about it, but she comes to acknowledge that she needs to pass on and fulfill her wish for everyone else to move on. Both were basically Obfuscating Stupidity as to find an excuse not to change the status quo and move on.