Now see thats not what you said in your OP you said "Then, he rejoins on another account named "cvissia" with 880 karma. I kicked him for duplicating accounts" so it seemed like you just kicked him as he joined but if what your saying is true about him mass rdming then no he shouldn't get Reg. But you said " I think when the second account joined" does that mean your not sure if it happened on the seconded account? or not sure on the karma he lost?
Nope. He joined, rdmed, and when I decided to make a reason I thought "duplicated accounts" was most fitting.
If not, he still commited and offense, warrenting a kick.
ONTOPIC: Seriously guys, this is his reg app, not arguement about why or anything. If you want to +1, so be it.