Multiple different accounts were created and used to upvote his own stuff and target other users with downvotes. This is the second or third time a user has been banned for vote manipulation, and as far as I can remember, the only reason aside from spamming that a user has ever been banned. Please do not create alts for the sole purpose of giving yourself more internet points, it's pointless and we will be able to find out if it's happening.
In the future, we could implement account restrictions to try and curb this. Currently we have no restrictions on freshly created accounts, other than sub creation and captchas for posting. We could maybe add up/downvote restrictions based on age of account or account level.
But yeah, thought it would be best to make a note of the banning rather than explain what happened in a couple of weeks if someone asked where he went.
PS: No, the irony of making this post on an admin alt is not lost on me.