A lovely idea in theory. However, it won't work in practice.
Let's imagine that I started being abusive to someone in Chatterbank and they clicked a button to block my posts. As soon as I realised that my posts weren't getting through, all I would have to do is to disconnect from the internet and then reconnect. (My ISP will then assign a fresh IP address to me, so that AB wouldn't recognise me when I came back to the site.). Then I simply re-register as a user. I could either choose a completely different username or, if I wanted to make it clear that the questioner couldn't get rid of me that easily , I could re-register as 'Buenchico2' or 'Bad Penny Chico'.
Chris