To be clear: I'm not claiming they don't ban users. They do. I've been told they don't shadowban users: they don't make it look like you're not banned while in reality your messages are all invisible to everyone but you... or so they've recently claimed.
AFAIK: "ban" and "shadow-ban" look the same: you can post comments, but they automatically [dead], the difference is just that if it's a "ban" you get told you are banned by a mod. And while it's probably a lot rarer nowadays, I believe e.g. the spam filter still automatically applies this without a message, it seems there is a system killing accounts that go too deep into negative karma, ...