Ah, the classic StackOverflow NaN test debate! Someone wrote a beautifully elegant isNaN() function that simply checks if a number isn't equal to itself ( num != num ), which is actually brilliant because that's the only time equality fails in JavaScript/Python. But then some principled developer comes along and declares it "prohibited witchcraft" despite admitting it works perfectly. This is coding purity culture at its finest. "Yes, your three-line solution works flawlessly, but I'm morally obligated to insist you use the official 50-line implementation with seventeen edge cases instead." The real witchcraft is how StackOverflow manages to turn elegant solutions into religious debates since 2009.