I had an admin contact me recently because they had deleted a test user that they had created, and when they did, they accidently clicked the “…and block the IP” button, which then blocked them from their own forum. Had they been the only admin, they’d have had to fix this from the console (which FWIW, I don’t know how to do offhand and a quick search yields no answer for).
I’m a bit surprised that this particular way of shooting yourself in the foot doesn’t come up more. That button does look pretty scary, though.