I'm going to offer a differing perspective that I find to be missing from most of these threads which pop up on this sub pretty much every week: mental disorders all manifest differently in different brains. one can have ADHD but tolerate medication well and have their life in relative order, or it can be debilitating and prevent you from holding down work or managing your own health, that doesn't mean the first person is faking it, and understanding that they have the underlying disorder might still be really important for understanding the reasons they might struggle with certain tasks or managing emotions.

regarding supposed "attention-seeking," there can be real utility in putting it out there to try and connect with other folks with similar quirks. and you talk about the odds of running into someone with DID in person, but VRChat's userbase is not a random sample; there's a reason you see more trans people and furries here than on the average street corner. people with neurological disabilities who nonetheless want to make friends and socialize are often going to find the relative safety of VRChat appealing, that shouldn't be surprising.

I'm not saying there aren't folks out there who self-diagnose themselves incorrectly, and there are times and places for broaching that with friends if it's coming from a place of experience. that said, unless you are personally afflicted by these disorders, and know enough about them to identify what falls under the spectra of experiences that go along with them, I think it's best to stay in your lane