It says "Deactivated Account": http://sleepymaid.deviantart.com/

So I guess it's voluntary account closure? Why so?

(On another note, I hate the fact that dA gives no public reason for banned accounts - it feels very Orwellian to see a controversial comment from a account that was simply "banned".)

I have no idea. o.O
Especially since his MC comic is supposedly now completely SFW, I'd think he'd embrace the DA community for its sake. I wonder what happened.

Pertaining to your side note: a lot of sites/businesses do that. Who needs to know the reason for the ban other than the administration and the banned account's holder? In most sites, you simply won't know they're banned. In this one, it's just more apparent that they are since you're outright told. It's a perception thing.

Yes, the crappy ones. But some are very honest at it: Youtube for example, it will tell you something like "sorry, this video has been taken down due to a copyright claim from XYZ Media Conglomerate", which is IMO very sincere from them.

And of course they have to tell you that the user has been banned somehow, because if you went to somebannedguy.deviantart.com and it just redirects you somewhere else silently, it'd be seen like a bug.

Nevermind the fact that there is no "report as spam" button anywhere, for comments or accounts... I've seen some.

But yeah, when I first saw dA, I thought it was much better than what it actually is.

Regarding Sleepymaid, I wonder what might have happened.

You could possibly ask him/her on Sleepychan. Probably in the /meta/ section.