For those long-time fabbers who remember me, thanks for the shout out :)! I don't want to belabor my point, but wanted to clarify my thinking, esp in response to a few comments: In any sort of group, the dominant mode of thinking/behaving at the individual level becomes the social norm.
So if you have a group of 100 people who form a community (whether online or in-person), and 95 of them think/behave in a similar way that clusters together on one side of the thinking/behaving continuum (i.e., there can be diversity or heterogeneity within the group, naturally, but there is a clustering of the similarly-minded), then that majority will create a social norm. And then the other 5 people who aren't clustering around that norm will automatically, by definition, be outliers.
There doesn't need to be any explicit bias or openly stated negative, critical judgment at the individual level for norms to be created and then enforced--social norms just arise automatically within social groups, and then over time norms are upheld. So a bunch of people all thinking similarly and holding similar beliefs and behaving (e.g., dressing) in similar ways (note I'm not saying the same, but similar) will automatically create a norm. There is nothing inherently good or bad about norms, they just are.
And to be part of the majority/norm feels comfortable, such that you might not even notice there is a norm :). There is a sense of belonging and of feeling understood, which feels really good. And to be an outlier can feel less comfortable, or even uncomfortable, and there may be less of a sense of belonging. Because you are distinctly different from the norm, by definition.
So, to connect all of this directly to YLF (can you tell I'm a social scientist who enjoys rambling on about these sorts of social processes? lol): Yes, of course, there is diversity in terms of what people wear, because it would be impossible for everyone to dress identically, like identical twins or something (though I'm sure there is an online forum for that!). But, if the vast majority of individual people who post on the YLF forum favor dressing in ways that aren't oversized, or favor more classic silhouettes--and emphasize that this is their personal, individual preference, of course--then all of these individual preferences will together be the norm. So someone like Irina (or me, if I posted my WIWs), who wears oversized clothes, will be the outlier. And being an outlier just isn't as comfortable, as I noted above.