There is a significant difference between sarcasm meant to insult, and sarcasm meant to be playful humor with a point. Common uses of sarcasm include witty or playful language, humorous banter, the expression of frustration at unfortunate events, self-deprecation, and as a coping mechanism for difficult situations. I see that you couldn't tell the difference in that situation, but trust me, that person was not insulting you. They included themselves in the joke.
The language is clear and unambiguous, and is intended to set a floor for the caliber and quality of discussion here.
I take your point, but the humor, if it was that, was made clumsily and was not well received. It’s not just me who felt that way; it was downvoted and eventually killed.