Don’t sweat it. You’d have to create a profile on each instance and then create all of the subs on each. And some have decent bot protection, so that is tougher. Then if they’re not active and you want one, start/find it on your home instance and petition your home instance’s admins for mod control. They’ll probably see whats going on and cut that power(-crazy) user off.
It’s not like Reddit where there’s only one version of a community. It’s a double-edged sword, this feature, but in your case it’s a clear benefit.