After looking at this for a few minutes, I still don't understand what it is. Where's the anti-spam system? I thought there would be a write-up outlining the anti-junk algorithm.
If you're powerful and get 100 emails a day for things that take up your time, you don't want to read 95 of them, but do want those 5 that matter to still be sent to you, by people who are confident enough that their email is important.
> CAPTCHA that stops Humans
> Yes, it stops bots too.
The reason spam is everywhere is that the cost of sending spam is low. The solution proposed by rePOWCHA is to increase the cost. It's a form of proof-of-work.