I'm still learning the ins and outs of this place and the others, but part of me thought that was the feature of being federated. User accounts could seamlessly transfer from one instance to another.
Looking further into it, it looks like that feature exists for content, but not so much for accounts.
I've been having constant issues connecting to lemmy.world for around a week now. Normally its "webpage is unresponsive" errors. Others like lemmy.ml have been loading fast and easily for me.