We all know IF often lets you customize the MC’s appearance. Like their hair, eyes, height, etc. I’ve seen some people say they want choices to have more of an effect on the story, but to what extent? And at what point would it start to bother you?
(Examples removed as they look to derail the topic.)
Those are bad exemples…
Redhead being smart? So blonde is dumb? Old stereotype that need to die.
Short vs Tall? Thats the reality of many peoples. Bad bad bad!
And green eyes as more appealing? Again, already in reality, where white is the best skin! Being white mean everyone love you! 
Anyway, in one of my game I wanted to play with Heigh. So I made it that females were taller than male. Outside of that, it didn’t have anything else going for it.
It only effected a few things, like at some point a companion will have to carry the mc and if its a female…considering she was tall it be different than carrying her counterpart the male who was way shorter than she was.
In a story, I did enjoy playing with heigh. Mostly small little things, like the mc was tall and her romance was short. So I had to pay attention at their actions when I wrote them. Like touching the mc forehead? When you are short, you can’t do it like if they are the same heigh. So had to write something cute about the mc bending a little so her romance could do that.
If I were to take the exemple of haircolor? I would play around the idea for exemple like in Naruto (A manga and Anime) where member of a clans had redhair. So you could recognize them easily. Same with eyes colors. Like you could say '‘This tribes all the males have gray eyes were the womens have blue eyes’. Or the male have long redhair, where the womens have short black hair.
But it isn’t just physical thing. It can also be others things.
Like you can play with someone attire (Clothes), or Mannerism. Or anything really, they are all part of customization.
Like in one of my story, a Tribe had this tradition of the Queen naming their 1st child after themself and the 1st child is always a female like the Queen.
Or the 2nd tribe has it that all the warrior wore mask and never showed their faces to outsiders.
So you know? There are endless possibilities.
I like subtle stuff. Doesn’t have to be big, doesn’t have to be spammed. Small details here and there, are better than over doing it.
But thats just me.
I don’t think appearance should change a whole lot, personally, and certainly not the worldviews of other characters.
A mention here or there is fine by me, like when you’re describing a particular scene that’s meant to capture the reader’s attention.
I do like it when tall characters mention how short my MC is, though, and vice versa.
I think you’re taking the examples I provided a bit too literally. Like I said, hypothetically, they would be things that would be believed by people in the story world, not the author. It obviously wouldn’t mean said fictional characters were correct in their assessment. It’s just that some people might like to include or interact with things like local superstitions for the sake of immersion and replayability.
Look be it in real life or in a game, or in a movie, or in a story, or in a book.
I wouldn’t play, read, or buy such a thing. I skip it. I do not care for that Immersion that immitate the shit I have to go through on a daily basis.
That’s all well and good, I’m certainly not trying to police how you read. I just wanted to clarify that the hypotheticals I tossed out wouldn’t be reflective of the author’s own opinion on people’s appearances. Just something characters in-universe would think.
And again, I’m telling and informing you that around here customization should never have any tie to oppression or racism of any kind. And saying ‘It’s for immersion, it adds replayability’…ain’t good enough.
But you do you.
Finally someone talks about it.
For me personaly, it would be great.
It adds to immersion and overall realism as people are what they are.
And however one might not like it, we judge based on what we know.
So, when You say that this particular group of people have the belief that Readheads are intelligent and have “reasons” for that
(That part is very important tho. They have to have reasons for that, like:
Most of notable/smart/intelligent people of their history happen to be a redhead)
And therefore most of redheads are initially trated with admiration/envy/loyality/kindness etc etc. as long as they don’t shatter that belifef by doing something stupid/dangerous/against the people which admire them,
Then such use of MC’s looks is just great.
(Tho one must remember that there will always be persons who won’t follow what is commonly believed and thus not everyone should treat redheads better/worse.
But that is more of minority than majority)
Like seriously, CYOA stories are RPGs.
No matter the genre of a particular GameBook,
There .is. Roleplaying involved.
And what kind of rolplay ignores apperance?
Scary looking man with scars on his face, and sword/(any other weapon fitting the story genre) will make others react more carefully to him.
(Maby he is a bandid, and those ate scarrs that his victims inflicted!?- No, not really he is gentle, kind and honest farmer, that had been attacted by a wolf in the past, and lost his wife, so he doesn’t smile.
But people won’t know that. And won’t care until somehow they learn the truth.
In their eyes, based on how the man look he most likely is a bandid and they will treat him accordingly to this belief.
Apperance not only aesthtics really.
Imagine You chosed to play a really tall MC.
It’s great. You can see better in crowds. You can intimidate more easyly. You can be a human shild to your companions. Reach highier spaces.
BUT.
You’re easier to target. Maby have more of a hard time hiding as You’re easier to spot.
You can’t fit in places your smaller companins can, and so You need their help.
Again You can be quite intimidating, which isin’t always what You want.
So with this examples its only natural others react to You accordingly.
Yes even if it’s just a hair color.
Predjudice exists. First expression exists.
It’s common.
It’s a primitive mechanism we humans have and mostly listen to, until proven wrong.
So yeah, I would love that if Gamebooks used our apperance more often.
Maby in one moment in the game being a blonde helps in beating a story section the easy way, because people assume we’re stupid.
And we’re not, but will use it to our adventage anyway
But in another situation, it can lock out certain paths/action that we are given. Exactly because we are considered to be stupid at first and have to prove ourselves smart.
Same with height/weight/disabilities etc
I understand though that such a thing could be a pain in the ass to implement in script especially if one wanted to make it complex and not 2 dimensional, so it’s okay if authors don’t try it.
But damn, it would be cool if they do
I don’t believe it should affect the story at all unless it’s the narrative/intention of the story, but perhaps you could have a villain mention a one-liner on the character’s appearance as an insult for example.
I like flavor text to acknowledge MC customization even in a small way. I don’t think appearance should determine how a story plays out, however, unless it’s more or less what the story is about and the author has something important to say with it, meaning they give it the proper delicacy such a subject should be given. A little more involved acknowledgement of MC’s appearance works, too. For example, right now, in a game I’m working on, a certain combination of hair color+hair style could trigger one of the ROs because of a person in his past who looks similar to MC. It won’t block the romance or change anything about the game, but it makes MC’s appearance mean something beyond some fun character customization.
Depends on the story, but I think the MC’s appearance should be mentioned every now and then so the MC feels like an actual character in the world instead of an onlooker. Dont go the Cyberpunk route of character creation/customization, go down the Skyrim path lol.
Its nice to have my MC feel ackowledged within the story.
Some minor interactions only, like if MC is short some taller character can help getting things off top shelf(cuz that’s just adorable).
That is unless trait has some narrative significance( like having horns or something in middle of a religious faction) then it should be appropriately reference be it good or bad interactions.
I always dislike it when my MC’s appearance feels jarring in comparison to the appearance of a blood relative (looking at you, Cousland family), so some re-occurring traits are appreciated. For example, sharing an eye or hair color with your parent/sibling.
It’s nice if relevant details are included in romances. If my MC has red hair and a specific RO has a known thing for redheads, it should be acknowledged that my MC is exactly their type (looking at you, Iron Bull). It’s also neat when particular height differences (or similarities) are taken into account during romance scenes. For example, when the MC or the RO has to go on their tip toes for a kiss. That can be cute as hell. Similarly, some very tall ROs might not used to being in a relationship with someone who’s equally tall.
I also liked it when, in Dragon Age: Origins, a banter appeared in which Alistair and Oghren talk about human/dwarf intercourse if you romance Alistair with one. Typical Oghren: “So, uh, what did you do with her legs? […] That’s the problem with dwarven legs. They’re useless as an accessory. […] Ah, say no more. Just got 'em outta the way and went about your business. Good on you, son.” 
Depends on the setting, I think. If the character is visibly different from the majority of the setting’s characters, it should affect it, I think, and it can be an interesting tool to use.
For the most part, I think, the appearance should be used in subtle details (like the character being too short to reach for the upper shelves, RO mentioning their features and so on). That’s why I’ve decided on no customisation for my on wip lol
When I always think of appearance having Some sort of effect, I think, in combat. Your height and body type can affect your fighting style, I, the forgotten one comes to mind. But to me, at least, unless your appearance is going to be used in flavor text, or for some other purpose, I don’t really see the point in offering that option in the story at all, just let the reader head canon it, if you’re not going to use appearance for anything. it saves you from having to do extra work
I haven’t played a game where I thought to myself “Jeez, I wish MCs appearance would matter less” yet
More flavour text is always nice but like Sujan said, the more relevant you’ll make MCs appearance the more variations you’ll have to write. Bacondoneright games are a good example of how to do it to make these stats matter and not go insane.
But if you’ve got a vision for how that would look and play like you should stick by it.
Another good way to implement appearance mattering is: the choice of MC’s attractiveness or the impression their appearance usually makes.
So short answer to OP question: as much as you want to and can handle.
I think it depends on if MC’s appearance will move the story. Like are they considered ‘ugly’ and that’s why they have a low self esteem/are bullied/is hard for them to find a partner.
If their appearance isn’t important for the story, there is no need to call attention to it. And honestly, when i’m reading, i can hardly remember how my MC looks like.
I think it should just be flavor text unless you want to dive into more serious themes (ex. racism for POC MCs, sexism, underestimating certain groups, etc). But this can be hard to implement, since not all players will make there characters apart of these groups you decide to dive into. It just makes more coding stuff, so I wouldn’t do it if it isn’t something you really want to explore
Depends on the setting and the characters.