That to me is why the cards and rep are silly things, because you can harass someone without revealing who you are. Imo every ban should be undersigned by someone and technically you should get a notification too (although that kinda fails to match up well in the case where someone gets banned and blocked from their PMs too).
The cards come with an automated PM.
You can ban in the control panel without notification, though the mod's name is attached to it on the ban list for the duration of the ban. I don't think there's a permanent record that way, though usually mods who use it will post about it in the mod forum so the others know the score.
The rep is signed, but it's set up so that only managers (I think) can view them. It was all hidden until I found that setting after someone complained about getting abuse. Do we have any managers currently? If not, the mods might get Marty to change that permission for regular mods. Should regular users be able to see it? Probably, but I don't think it's a big deal. I'm not a big fan of rep as a system, but I don't think it's been much of a problem here.
Can't you access your PMs if you're banned? That's a bit of a flaw in the system.