Display Reason for Automatic Blocks by System

[probus]

This has come up before..

https://meta.discourse.org/t/who-is-banning-my-users/42628/

Users Automatically Blocked by System

I have noticed that the system automatically blocks some new users. These appear to be normal users who don’t have the same IP as anyone else and in most cases haven’t posted a single thing. Why are these users blocked?