Answer: Hey, @3iuu-na!
So we are afraid this is just one of those hard facts true of any part of the internet. While we have some tools in place to stop people from doing this in the obvious ways, it’s incredibly difficult to prevent all of the ways, so we’re not perfect.
We are not aware, in fact, of any platform on the internet that can successfully fully stop someone from making another account if they’re determined enough. (Unless they shut off new account creation entirely for everyone.) The only thing that’s kind of comparable here is how Netflix is currently trying to stop people from using the same account in multiple locations, which is the opposite of this problem and has just as much technical difficulty to get right.
But we couldn’t agree more in principle: banned users should not be able to create new accounts. We are not sure we can prevent them from doing this in all cases. Regardless, if you see somebody awful making a comeback in a new account and doing bad things, please report them! We’ll happily ban them again.