I run my own instance and I can reply, make new posts, and even moderate communities on any instance I follow, and that doesn’t block me instance from joining. The only thing I cannot do is create communities on other instances.
So when lemmy.ml went down do to server load I had no idea until i clicked a direct link to it. I could still see my copies of their communities.
It’s more like my account won’t ever be deleted if the sever I signed up on goes away.
It will be interesting to see what happens as large instances grow and how they deal with storage and bandwidth. Any media a user uploads anywhere is hosted on their main instance. Self hosting also puts me in control of my upload media.
Anything been taken over by the admins and turned back on yet?