Can't say I know how to close an account, or if you're even given the option to, but I do just want to say somethin'...
You could stick around and not talk about SB, Nick or cartoons in general...just a thought. I mean, I'm sure there're tons of members around here who also don't care much for talking about those sorts of things anymore but stick around for the community anyway; pretty easy for members - regardless of interest - to integrate themselves into the community via the Nautical Nonsense forum even if a member wasn't exactly well-known already in the community or didn't post much prior.
So...I dunno. It's your decision, ultimately, so I'm not gonna push. If you can't close your account and have no interest in coming back, then I'd recommend just logging out and never logging back in again - that'd be an effective way of 'closing' your account, or at least providing yourself with a sense of closure from the site.
We only delete accounts if it is for privacy issues. If you're trying to stay clear away from Nick and Cartoons in general..I can change your login name, password, and details of the profile and that would be the end of that. All you would have to do is register again if you ever decide to come back.