The Santa question was closed without making the reason explicit in the comments: should the Santa question be allowed here? If not - why not?
I was going to add a comment, but I think the format is more proper for an answer of its own, and I think it does answer the question, so bear with me that this answer references another answer.
3: an exception to our usual sternness is only going to be beneficial to the community.
This argument is the exact reason why I reacted strongly against this question. I'm sorry if I'm getting personal here, but being a moderator does entail elevated personal responsibility, so I think it's called for. I think that few have been driving this sternness as extensively as yourself, Sklivvz, relating over and over how detrimental it is to the community to allow a single poor question, as it lowers the bar for the entire site.
With that in mind, I was appalled to see that you of all people would go ahead and post such a question, and comment to close voters that they lacked a sense of humor. As a moderator, you should post better questions than everybody else. Your responsibility in setting the standards here are higher than that of anyone else. If I see a random person publicly and overtly violating the law in some regards, I might assume that that was a reckless person, and that there was only coincidentally no police around to enforce that law. If I see a high profile politician perform the same act just as overtly, however, I might instead be inclined to consider that perhaps it is I who have misunderstood the law in the first place. If a moderator posts these questions, they must be OK.
And I really must add that the perseverance with which this question makes the whole thing worse as well, as exemplified by the comment about close voters lacking a sense of humor. To my mind, this disqualifies the question even further, as it doesn't even meet the questionable objective that it was created for (i.e. it produced discord rather than light-hearted enjoyment).
1: the question is notable
2: similarly obvious questions have been allowed in the past
All your example of other allowed questions are questions that are about topics at the very heart of skepticism. Creationism, conspiracy theories and woo woo are the very cornerstones of pseudo-science that plague the scientific community. These are the very reasons that scientific skepticism came into existence. These claims all have adherents among the influential grown-up otherwise-educated public that will tenaciously defend their truth values, and as skeptics, we have a commitment to question these claims.
The same is in no way true for your Santa question. Santa Claus is an invention intended to entertain kids. When we tell our children that Santa Claus exists, we don't even intend for them to grow up believing this.
I do not agree that the existence of Santa Claus is a noted and well adhered to belief among legally competent adults, as is – sadly – the case with ghosts.
My verdict is that this question should be closed and possibly be deleted not only because of its inherently poor quality but also because of the example it sets by being a question posted by one of the community's trusted moderators who have personally pushed the sternness agenda to new extremes as it applies to questions other than his own.
I wasn't a fan of the question from the beginning, but I didn't feel strongly enough about it to act myself or start a discussion about it. The question is bending the rules quite a bit, and while I'm not categorically opposed to making the occasional exception, I don't want to create a precedent here.
It's far more consistent to disallow joke questions entirely, I really don't want to get into the argument later, why other questions of that kind are closed and a moderator was allowed to post one. That discussion won't lead to anything constructive.
So, I think the question should be closed.
Really? We can't let our hair down once a year?
To be clear it is, I believe, obvious to everyone that this is a question intended to be humourous. It is equally obvious that the normal standards don't apply. The only question is - do we want to allow a humourous question once or twice a year. The inventiveness of the answers clearly indicates that many Skeptics have warmed to the idea.
There is of course the danger that we get a wave of humorous questions that threaten to engulf the site, or that people ask offensive questions claiming this as precedent, but frankly that hasn't happened. We can deal with it when it does. To ban ALL questions like this is like deciding not to eat any food at all, because too much makes you fat.