(Upvoted because transparency is valuable and to be encouraged.)

Will Newsome is a poster with known mental problems and the possibility that he's making fake accounts is one I've considered before.

He almost certainly has or had fake accounts at various times. I think I've even suggested banning him for that violation. That said, Will's claim that he has not upvoted his own posts via sockpuppets is entirely believable. Take action against Will if necessary for whatever other reason (like a track record of active, insane trolling) but if action is taken against him based on the assumption that a positive reception of his contribution must be fake that would be troubling.

and seems like a no-brainer to ban before it happens again.

Making decisions 'no-brainers' is easy if one is willing to disassociate oneself from the consequences.