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.
That’s entirely up to you, it can be the same username if you want. Speaking as an instance admin, there is no problem with users creating multiple accounts across instances, even if they’re the same username.
Spam would be creating as many usernames as you can on any given instance (e.g. trying to register 100 users on lemmy.world because reasons) - there’s obviously a problem with that. Creating you@instance1, you@instance2 and you@instanceN is perfectly fine.
That’s actually likely to cause some issues down the line with people impersonating other users, but for now It’s fine
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.
Not at all. You don’t have to identify as yourself on every instance you have an account. It’s literally a different account. You can keep a backup of all your subscriptions/follows/etc from one to the other or you can treat them as two entirely different identities. Just don’t have them generate a lot of pointless traffic between each other (like arguing with yourself on a post or something).
Wouldn’t it be easier to be the same person across all of the communities and instances rather than split your personality?
In the Fediverse it isn’t possible to reserve your username. I could host a server and get something like favrion@lemmy.account
so it’s unreasonable to expect that users keep the same username across instances. Reddit is more anonymous than Facebook. The Fediverse is more anonymous than Reddit.