Well, it clearly states in the rules that you are only allowed one account. And as far as I know, me reporting them is just me following the rules of this game.
They may not be able to find a list of things they can do to get banned, but they can read the directions, which is a common mistake in this generation. I can see if you forgot your password or something, and didn't know how to contact (even though, again, read: there's a contact tab) the game creators to reset it, so they create another account. But this guy played with both accounts REPEATEDLY, ADMITTED to me about his multi's (see chat in original post), and lied to me about having them the next time I asked.
So obviously he knew you weren't allowed to have multiple accounts, seeing he used both of them. It's like he was asking for a ban.
The game's population is partially getting smaller due to multiple accounts. But relax, it's 8-16 days (depending on your ban) for multiple accounts, so they should suck it up and wait. Also, they should read the rules next time because it clearly states only one account per person.