The "personality" and "private background" fields on a character are only ever viewable by staff and yourself, so their main intended reason is to give staff a way to understand your character. However, the public background can be seen by other players if they investigate through the rumor system, such as asking VNPCs about the character.
These explanations don't need to be exhaustive, even though it can be helpful for staff to have access to a comprehensive amount of general information about your character, such as why they have the motivations they do, do they have family still alive, and so on.
But mostly, there's a lot of flexibility in terms of how a player wants to document the character's background. You could roll into the game with a declaration of amnesia if you wanted, or something as short and simple as one of the automatically-generated backgrounds, or you could put in a lengthy and richly-detailed work of artful prose, or a set of bullet points of important facts, or whatever you like (within reason).
Anyway, you can put in a quick summary, and then edit with more important points as you continue to play. But in general, the things written in your background are what you can expect staff to know about your character's past when they are responding to your active stories. We don't need to know absolutely everything, and you can certainly put in more as you think of more, and add completed story events at a reasonable sort of character development pace. You can submit a petition if there's something really important that needs to be added or corrected to your background and you're out of background changes, or suggest a CHANGE to your character. The CHANGE command lets you specifically request an unlimited number of changes to most character attributes, but it requires staff review, unlike these quick extra changes/updates that you can do with limited opportunities and will take effect immediately without staff approval.
Originally, we didn't have any way to change backgrounds when coming out of chargen -- but we added those three extra initial changes because sometimes people aren't able to really "get into" the character at all before actually roleplaying. Personally, I've rolled into games with amnesiac characters before (or just extraordinarily bland archetypes) and sorted out things through the course of playing the game. Most games I've played have no way to edit backgrounds at all, and this has never stopped me from developing a more detailed character -- and conversely, just because we have a way to edit backgrounds here, it shouldn't stop you from developing more detail.
Because Song is such a story-focused game, the background is genuinely important. But requiring it in full right away can be very intimidating to someone who (like me), tends to be unable to really know the mindset of a character before actually playing them through a few IC experiences. So, that is why it's possible to change backgrounds coming right out of chargen; not because we expect it or require backgrounds to be consistently updated about small characteristics when it's ultimately unnecessary. It sounds like you already have a pretty good idea of the general facts of your character's background, and that is certainly sufficient!
The limited pace of being able to change the backgrounds is primarily because we'd like players to focus their character development energy through the Story system. For example, in the showcase series, (Chapter 8) Emmaline's background never mentioned Mira's Special Stew -- that was something that a player could've come up with on the spot. And it wasn't necessary to add this information to Emmaline's background, but it was an instrumental little plot point through her story arc of feeling at home in Omrazir. Maybe after her birthday, though, Emmaline could update her background to say something like "Mira used to make a special stew when Emmaline was small, and when Emmaline was feeling lonely and dejected, she found the way to make it in Omrazir, which made her feel more at home." That could be an addition to the private background, while an addition to Emmaline's public background would probably include something like, "Emmaline might be known on the street as one of the initial founders of the Omrazi chapter of the Bardic Fellowship."
That's the main way that we expect players to be updating their backgrounds, as time goes on. We don't really want these updates to become a required chore for players over every detail, or something that admin need to check every single time they address a story arc. (Another lesser reason for allowing only limited changes is to prevent potential abuse of the rumor system, as well as preventing a situation of staff being confounded over constant updates while trying to run plots.) The intended purpose of backgrounds, and updates, is that they can be useful ways to summarize large amounts of information, information that is all already in the past. You can definitely use cutscenes to add logs of past situations to your story arcs, as well as logs of using the REMEMBER command for particular memories. You could update your backgrounds periodically with important things whenever you had the chance.
I also want to note that we sincerely appreciate your attention to detail, and care for the lore, and I am really looking forward to opening with such an awesome group of players. I almost don't want to type that so as not to jinx it, but sometimes it's important to convey appreciation so people don't feel like their questions are a bother at all. I actually found a pretty huge oversight in background-updating in-game commands while looking through the related code because of this post, and am now fixing that, so we are really benefiting from your engaged involvement here.
TLDR: These sorts of modifications should just be rolled into the limited allowed changes.
