Let's talk about child avatar criteria for a moment.
This is Juno, my little in-world sister. Little as in one year younger. What she's wearing is something she isn't too unlikely to wear these days. It's still quite chilly outside after all.
Those of you who know her won't doubt that she's a grown-up woman. But there's a whole lot about her that may qualify her as an underage avatar. I'm not even joking.
Yes, on the one hand, protection against paedos and their unlawful ageplay is a necessity; see also Safine's most recent post:
https://opensimworld.com/post/108176
On the other hand, paedos are trying to circumvent countermeasures. Add to this the most recent drama about Lindens being directly involved in sexual ageplay in Second Life.
As a result, sim owners ramp up their countermeasures. This goes well beyond more and more sims redefining the Adult rating as "G-rated, but no child avatars allowed". It's likely that the signs that an avatar is underage will be "upgraded", too.
And the wide-spread anti-underage paranoia has made them absolutely ridiculous quite a while ago already. There's so much that could qualify Juno here as a kid.
Let me sum it up.
First of all, her height. The most blatant sign and the only one that triggers auto-bans. She's "only" 1.74m which is 5'8½". Many childgates still run on default settings which ban everyone under 1.80m. And I guess their number will increase as more and more sim owners decide that 1.60m or 1.70m doesn't cut it anymore. I'm pretty sure Juno has fallen victim to childgates twice already.
The other criteria are purely visual.
Her shape is somewhat close to realistic. Her head is about ⅛ of her body height which is actually still a bit small for a real-life woman. By OpenSim standards, however, her head is rather large in comparison with her body height. This reeks of a kid shape.
Next, look at her skin tone. In early April in real life, this is a fairly typical skin tone. In OpenSim, however, grown-ups are basically required to have a deep tan. Even most goths have darker skins than Juno. The only avatars with such light skins are child avatars. Well, and Juno, but if you don't know her, you're easy to take her for a kid because her skin is so light.
Now, look at her face. Look at her lips. No pumped-up boat lips. This is what real-life lips look like, but in OpenSim, the only avatars with such thin lips are either male avatars or child avatars. Since she doesn't have a perma-stubble or a full beard, she can't be the former.
Anything else you notice about her face? Right, no make-up whatsoever. Practically all other adult female avatars out there at least wear lipstick. She doesn't even wear that. Well, sometimes she does, but not here, not now. Makes her look like a kid in comparison.
Speaking of make-up, look at her hands. No nail polish. AFAIK, not a single one of the popular female mesh bodies lets you go without nail polish. Especially Athena doesn't. So basically, if a female avatar doesn't wear nail polish, it's either a classic, mesh-less layer-and-prim avatar from, like, 2007 or a child avatar. And Juno doesn't look like she doesn't have a mesh body.
And her hair? Yes, that's a bob. In real life, it was a rather popular hairstyle in the 1960s. In OpenSim, hair significantly shorter than shoulder length is probably the second-most child-like girl hairstyle right after twin pigtails. As an adult woman, she should be expected to have a long lush mane. I've never seen a single female avatar with Paige hair. Black could be a saving throw because little girls are usually blond, but not necessarily.
Let's continue with her clothes.
She's covering a whole lot of skin, more than almost all other female avatars. Granted, most little girl avatars show a whole lot more skin, too. Just look at those super-short skirts that seem to be a requirement for underage girl avatars. But grown-up female avatars are basically expected to do the same. Thus, covering up makes her look less adult.
So does the rather loose fit of her clothes. Adult female avatars may be allowed to wear long denim jeans, but only of the skin-tight kind. But while Juno's jeans are labelled slim fit, they look rather like something a little boy could wear.
Her pullover gives the impression that she doesn't have a waist. You know what other avatars don't have much of a waist? Good thing she doesn't have a petite body because there's no petite variant of her body, otherwise she'd look almost flat in this pullover. Also, that shade of teal might be questionable at least. It'd be worse if that pullover was pink, but she doesn't have it in pink.
Finally, her footwear. She's wearing flat shoes. Adult female avatars are expected to always walk around on 6" heels. In fact, she's even wearing sneakers. Flat sneakers. Even tip-toe sneakers are questionable, but unless worn by a manly man, they're little girl material.
And if that wasn't enough, she's wearing them with white socks. The only hosiery adult female avatars may wear in OpenSim is nylon stockings, Zettai Ryouiki-style, showing skin on the thighs above. Socks are pretty much exclusively worn by children, so what does that make Juno?
I bet that if Juno wore this to events in places whose owners don't know her, chances are she'd be banned on the spot for being a kid. Good thing her usual party styles are of the kind that causes her to be accused of dressing like a grandma instead.