I forget the source of this, but I read that it was by design. It was understood that inconsistent censorship and oppression was actually more effective than the consistent type.

Knowing exactly what you are not allowed to say can be comforting: You trust in the rules and there is no reason to be afraid.

Add in inconsistencies and suddenly this comfort is removed. It adds an extra layer of uncertainty and fear to everything. Two people can say the same thing and only one disappears. No one knows where the line lies. It's a nasty psychological game and quite sick and twisted actually.

you couldn't openly and clearly critique/satirize the whole System nor the Party nor the Leader (with all 3 being basically equivalent). You were allowed (and to some degree and in some shape encouraged) to critique and have a laugh at supposedly small and separate defects/impurities on the shining body of the System, the defects which were still present as supposedly exceptions and not the rule ("otdelnye nedostatki") thus your work would supposedly be improving the System instead of weakening it. The great talent of some of those writers, directors, actors, etc. was to show those supposedly small separate defects in the formally allowed way while really making it a deep and profound satire of the whole System.

The approach of course isn't unique to USSR, it has been the forced choice of artists through the history of ideological oppression in human civilization, and giving the rise of ideological intolerance everywhere today i expect to see again that approach more and more.

The books are very pro-Soviet. The satire is directed toward people who are considered to be "behind the times": a priest depicted to be not much priesty, the former "head of local nobility", and so on. But the main protagonist somehow came out so lively that we totally sympathize with him :)

Humor is a harmless pressure valve, why should those in power be worried by it?