I was mistakenly shadow banned on reddit one time. I didn't realize for like eight months.
I don't post that often, so it didn't really bother me. I remember being surprised I was getting no responses or any up or down votes for some comments during those months. But sometimes I posted messages and just forgot to check back. So I probably only noticed a couple times.
Anyway, one time I'm browsing reddit at work in a comment thread I know I posted in when I was at home and I don't see my message. I find out I'm shadow banned and after messaging the mods I was back to normal in a couple hours with the reason that it looks like I got swept up by the spam filter.
So, no, I don't really like the idea of automated punishments without notification.
The only reason lightning never strikes in the same place twice, is that the same place isn't there the second time.