Why do the instances keep going down? It makes me think that this is not a reliable social network, but the alternatives are not as good.
There are no requirements, and they wouldn’t be enforceable even if somebody tried. The admin of instance1 has no way of knowing that you already have an account on instance2. Your identifiable details (IP address, e-mail address) are private to the instance that you sign up with and it would be a violation of privacy (and inherently scummy) for those to be shared between instances - they’re not.
You can be anonymous on the fediverse, just like the Internet in general used to be before Facebook.
I choose not to be. I like to have a clear breadcrumb trail for myself and not confuse people.
I get that, I’ve been “SoNick” or some variation of it for a few decades now. However, a friend of mine uses different - but thematically similar - usernames for different services, when I asked her about it she explained that as a girl on the internet she has attracted more than a few stalkers; changing up the username makes it harder for them to find her on different services.
I personally don’t understand why people feel the inclination to pose as multiple accounts under different names. I used to use anonymity as revenge before I learned that it’s a way to hide your accountability for things that you may have said or done controversially. I didn’t make fake accounts after that. Use your name; claim that responsibility, restore your trust, and move forward. But that’s my opinion and may be unpopular.