First, the handclapping smiley was to sort of mock your post by doing exactly what you said was innapropriate.
But then, I realized that the handclapping alone could be considered rude. So I went with the most recognized smiley for such circumstances when you want to make it clear that your are just joking.
As for it (sarcasm) being the lowest form of wit... well... this is the interwebs. Even if you could do otherwise, you have to go for the lowest common denominator. Even on a website like HFBoards, where the discussions are actually polite, interesting and generally civilized. Even with all of that, you still have to assume that your interlocutor, or might I say, your interkeyboarder is just potentially plain dumb or not paying attention and thus, might not get the joke your are trying to, sometimes akwardly, pull. And that is the root of the problem. How can you possibly reconcile wits and brains in fruitful discussions when there might be this gulf of incomprehension always looming? Going for the simplest solution with the sarcasm smiley is the easy, but maybe suboptimal solution. You can also go with a lengthier post that textually detail your train of thought more precisely (even though precision does not always ensure accuracy). So, obviously, it's never easy to choose between the two approaches and I, for one, got that decision wrong on many occasions...