Sorry for a late reply.
I think it's a good observation to find those three warnings. I had not realized that, so I watched the arc again. Then, I got angry.
angry at the animators. Usually that warning was presented out of context. It's inevitable for viewers to get a wrong impression like "do not be kind to everybody, Araragi!".
1. Hanekawa.
The dialogue with Hanekawa in the anime is fine. But the problem is the anime already dropped most dialogue during the Araragi-Kanbaru date(?). So viewers should hear Hanekawa's comments without knowing what's really going on, though she made a point, anyhow.
In the novel, however, readers were already given an impression that Kanbaru will not threaten the relationship between Araragi and Senjogahara, at least for now. Knowing that, Hanekawa's words sound somewhat differently. As far as I understand, she was not only talking about Kanbaru, but also about herself.
2. Oshino.
Initially, I thought Oshino is an arrogant, frivolous and greedy lolicom (He's living with Shinobu and he did not charge Mayoi and Sengoku).
But it looks to me that Oshino's role in the story is to deliver the author's thought directly to readers, especially in the Nadeko arc. I will translate relevant part. Some of them overlaps with the anime.
Oshino: I have led a wandering lifer for a while, but it's first time to talk with a certain person for long. You have been continuously involved with oddities. Moreover, you tried respond to every oddity. It's odd, really. They say that once you are involved with oddity, you are more likely to be involved again. That might be true, but usually a person who experienced oddity tends to avoid it.
Araragi: ......
Oshino: By doing that, a balance will be kept. Earlier we talked about Tsundere who'd like to interfere with other people's business or take care of others. But isn't it about you, Araragi-kun. Well, but I don't think it really matters. I even envy Araragi-kun of that kind of personality. Sometimes I would talk grumpy about that, but your personality has its own merit. By the way, what will you do after I leave?
Araragi: Ah... Well.
Oshino: Oddity is always there as if it's natural, so it's not something to approach intentionally. If so, you will be an offender. Araragi-kun, you worry too much. It's overprotection. You tend to do something even if it's ok to leave them alone.
Araragi: Once I got to know, it can't be helped. I have already know a fact that the oddity exists, so I can't act as if I did not know them.
Oshino: Haha, would it be better for you to forget completely just like ClassRep-chan? It might suit to someone like you, Araragi-kun. Forgetting everything including Shinobu-chan...
Araragi: Forget everything... Impossible.
Oshino: Ah, Shinobu-chan. Ye. if I left, you should take care of Shinobu-chan. That's what you chose. Of course, you can abandon her if you want.
Araragi: Well.. Oshino.
Oshino: You should be careful all the time because she is not human. Don't develop strange empathy for her because she is a vampire. Her shape was changed, but the truth is unchanged.
Araragi: ...
Oshino: Was I grumpy? Take it easy. We are so close now, so I will not disappear without saying a goodbye. I am an adult, so I know what to do. But if you are thinking about your future after highschool, you'd be better to think about this work as well.
Araragi: Are you saying that it's irresponsible to save everyone you encounter? Hanekawa told me that it's irresponsible to be kind to everyone. But I can't be like you, Oshino. As you told, I am a 10% of vampire. I am oddity itself, so I can't be on the side of human who expels oddity.
Oshino: You don't have to think in that way. It's only about knowledge and know-how. Would it be cool to be a half-human-half-ghost ghost sweeper like a manga character?
Araragi: Even there is a specialist wearing Aloha shirts.
Oshino: What is more. Araragi-kun, if you want... whenver you abandon Shinobu-chan, you will be complete human. I hope you do not forget that.
Oh, It's much longer than expected. Anyway, if you look at the conversation carefully, Oshino never told that it's irresponsible to be kind. On the contrary, he rated Araragi's personality. During the conversation, Araragi suddenly remembered Hanekawa's comments.
3. Kanbaru
I think the Nadeko arc is similar to the Mayoi arc in terms of the development of characters. Senjogahara was introduced in the first arc, then her relationship with Araragi was settled in the next arc. Kanbaru was introduced in the third arc and her relationship with Araragi was settled in the following arc.
Considering this, can you imagine if the Mayoi arc was presented this way? All the dialogues between Senjogahara and Araragi are removed, both of them just solve the problem without any significant interaction, and then suddenly Araragi shouts "Senjogahara, tore!". The Nadeko arc was made like this.
Anyway, I will do some translation again. Unlike the Oshino dialogue, it was totally ignored in the anime. The talk happened during the ritual in the shrine.
Kanbaru: It's OK if Segoku-chan is healed, but Araragi-sempai, you really saves everyone who you encounters.
Araragi: No, it's not everyone. Well, it's as many as I can. Moreover, if it's a acquaintence, I am more concerned.
Kanbaru: I think Senjogahara-sempai likes Araragi-sempai with a kind personality. I also think that kindeness is what makes you attractive. Now I think it's fortunate that Senjogahara-sempai's boy friend is Araragi-sempai who has a kind personality. However, I have one thing to wish... If you face a situation that only one person can be chosen, please choose Senjogahara-sempai.
Araragi: ......
Kanbaru: It's up to you whether you sacrifice yourself or not. But I hope you treat Senjogahara-sempai most importantly. Well, I am not qualified to say this, anyway.
Araragi: Kanbaru, you are more than qualified to do that. Rather, because it's you, you can say that.
Kanbaru: Then, I am fine.
Araragi: As you said, I also think that it's fortunate that you are Senjogahara's kohai.
Kanbaru: Thanks for saying that.
There are lots of flirting and jokes exchanged between those two in this arc. But I think this conversation shows how things were settled. That is, Senjogahara first, Kanbaru second (eh?)
By doing so, Kanbaru also gives the answer that has bothered Araragi in this arc. I think it's a priority. You can save as many as you want, but before that you must set up your own priority.
To sum up, first, Hanekawa raised a question about a responsibility and kindness, which made Araragi uncomfortable for the whole arc. Second, as Oshino talked about independence and determination, Araragi, who were pressurized by the talk, reminded of Hanekawa's question and get stressed. Finally, settling the relationship, Kanbaru gave a clue for the answer, then proved it with her body.
That's my opinion about those issue.