It is Jared Clemens, aka dotdotcircle. The IP used in the attack has logged into his forum accounts as recently as today.
When you're talking about IP overlap and such, you have to consider the size of the user base. Blockland has ~7700 active users. This isn't some giant ocean of piss you can hide in like 4chan. This is a puddle of piss. The chances that two people live in the same town and have the same hobby of attacking servers via spoofed network traffic is basically zero.
Jared has been "leaving Blockland forever" since 2010. He last "left" about 6 months ago, but then just a few weeks ago he turned up to run apologetics for the Blockland cheat dll. And now he's flooding servers again.
He has never left. He's probably stuck in some sort of mental loop and will need therapy to actually free himself.