- The literal correctness. There really is no letter "f" in the string "spec".
- The indirect contradiction. "Spec" is short for "specification" and there is an "f" in that.
- The implied rudeness. See also There's Only One F in Fulham.
- The pun on the rudeness. As Homer says, it's funny cos it's (so often) true.
- The metaphorical contradiction. Even if there is no f-ing spec, or story, or whatever, there's always something you can base an investigation on.
- The number of interpretations and nuances I could find in it.
Part of our job as testers is to be able to recognise this kind of potential for ambiguity and multiplicity, maintain contradictory interpretations for as long as it's useful but then tease apart what can and should be separated when it makes sense to do so.
No F in spec? So what? There's an F in tester!