[alance]

I'm suggesting that one should not be able to obviously detect that they're being challenged.

Eg I could respond in Pig Latin to you right now because I can see that's what you're asking, but if that particular request were masked or hidden or behind a puzzle, and you received a Pig Latin response well, maybe it's a bot (or a capture the flag sort of a person)

[alance]

Oh! And if one felt like solving the puzzle, it might lead to that person being mis-identified as being a bot. Which would be a perverse incentive to avoid wrecking the trap.