I was fairly certain you have talked about some extensive homebrews for other races, I suppose I figured you had done more with the halflings.
Still, I've never really heard of the base halfling living in someone elses attic, or in backalleys. And I've never really heard of them taking the poorest and least paid jobs (typical level that chimney sweeps and ratcatchers were). Generally halflings are presented as shop owners or tavernowners. So, that is a bit of a difference.
The halflings delivering the mail is a bit different, nothing really mentioned for that anywhere. But I'm sure you just have them do that occasionally, and in no way in an organized enough fashion to be known as a reliable source for delivering the mail... because that would make them important. There is a reason the existence of the postal office is in the Constitution of the USA after all.
But, I think your phrasing of "core nature" is important. Because it seems that is what you think I'm out to change. And it isn't. Halflings being cheerful, genial, enjoying the comforts of life, and not being obsessed with wealth are all traits I'd like to keep. I'd like to add things like, say, halflings nomads delivering the mail, because it integrates them into the world. But, you keep telling me that doing things like that make them too important and therefore we can't do it.
I'll also note, that in the second post, you did exactly what I said in talking about your hombrew (though only very very briefly) in response to me asking about the PHB, and the second time was you deciding you needed to tell me about your homebrew, and I'm certain if I look around that area, once more, we'll find the discussion centered on "how are they presented in the PHB" to which, again, homebrew isn't how the game is presented in the PHB.