So if I understand this right, you pick a server and your server account can post on that server and any servers that that server federates with.
So what happens to your account if the server you joined goes down? Yes, you could always create a new account somewhere else, but you lose all your followed communities and post and comment histories as well.
That’s sounds like a good idea. Instances can be very diverse, I think it would be better to tag individual communities but all that’s hypothetical. At the moment, anything is better than nothing.