To avoid an edit war, since I still strongly disagree with your notion that making the distinction makes it more unclear when the very reason I changed it in the first place was because it currently is confusing and unclear.
For example, seeing that Rangi was listed as a deceased character confused me, as she's a Kyoshi novel character, which thus firstly struck me as being a major spoiler, before thinking indeed "right, currently timeline". If I already wondered about, what will a user with less knowledge about the workings of the wiki say about it? The easy solution is to just make the distinction per show/book from where we know the character from. That also instantly gives the additional added value that you from where those characters came from. I could agree with the notion that it's too OOU (although we use it on the bending pages as well), but then I would counter that we can just easily put some dates then, because being "notable" by itself is also very subjective and time-bound.
Also, if you throw them all together, we basically need to list everyone, save for the TLoK characters, as dead, which makes it a very redundant thing to do.
So if we want to keep those lists clear logical, we should either insert a distinction to indicate in which time period a certain character is considered to be deceased or we should just do away with the deceased indication altogether.
Another bonus to have the distinction per time period is that it allows you to indicate character movements. Take Aang for example, he's a notable Southern Air Temple figure in ATLA but also a notable Republic City in TLoK. You and I know that because we know the series by heart and know how those pages word. Other people do not, which is confusing.
Simply put, I feel differently; for me, seeing characters listed several times, not to mention characters who lived at the same time split into different sections (Kyoshi's daughter Koko, for example, who lived during Kyoshi's time, but is not listed in the novel section as she was born after the novels - yet stll hundreds of years before ATLA) seems extremely odd and IMO confusing. I see your point, but it is probably an issue of perception and thus subjective.
I also think that people moving from one place to another is not an issue at all. Today, many people have several areas they regard as homes or are otherwise attached to. In the Avatar universe, the same is true: Kyoshi herself was not born on Kyoshi Island, and neither was Jianzhu, yet both regarded it as their home. The same is true about Aang and others such as Katara: Katara spent much of her adult life away from the South Pole, and clearly saw Air Temple Island as her home, yet always remained attached to the Southern Tribe, even spending her later years there. To list Aang as person of the Southern Temple in ATLA, but as Republic City citizen in LOK would downplay these dual loyalities and attachements, and I think that we shouldn't do this.
Other than the issue in regards of people being listed as deceased, unified in-universe lists seem to have worked for the past years; I feel that they should remain as they are - except extremely long lists (such as with benders).
In fact, however, I strongly agree with removing the deceased indication from the lists. Since Lao Ge and some other characters such as Tienhai have appeared who have showcased that immortality is possible and mortality can be fluid in the Avatar universe, these indications have become flawed anyway (how should one list Iroh or the Painted Lady, for example? They are not dead in the truest sense). In addition, we might get more novels / comics about past Avatars in the future which would bring even more confusion to the lists.
In addition, as you brought "notability" up: We should probably discuss who is "notable" in regards to the nation articles; for example, the list of characters on the Earth Kingdom article is extremely arbitrary. We should clarify whether "major" characters in the shows, novels, and comics should be listed or characters who were important in-universe. As an example: The 46th Earth King is an extremely minor character in the shows, yet very important for the Earth Kingdom's history.