We desysoped a couple of people in the past year. Some on en, a serious lot on de, very recently on ja. And a good bunch of tired wikipedians in need of a break.
In short, except for urgency, no desysoping should take place on the english wikipedia without first arbcom decision.
This deference of the privileged to the privleged is apalling. 172 should have been desysopped the first time he unblocked himself. It is not a difficult evidentiary matter, and desysopping is not as severe as blocking someone,which any sysop is allowed to do. After sysop powers are just a privlege, an opportunity to serve. It might even be a good idea to sunset sysop powers, say every three months (although not all sysops at once) to see if the sysop can get elected again.
172 had been engaged in other abuses of his sysop power, and had even been disciplined by the arb committee (as a user not a sysop I believe), but desysoping him (or her) should be been an easy and trivial addition to the discipline at that time. It is not like sysop powers are some right.
-- Silverback